I am having the same problem, and found out it is because /system/bin/fsck.exfat segfaults. Here are the relevant parts of logcat:
D/MemorySettings( 7159): Storage : Montar cartão SD
D/MountService( 2127): :::: mountVolume :: path = /mnt/extSdCard from pid = 7159
D/MountService( 2127): doMountVolume :: Mouting path = /mnt/extSdCard with = mounting
D/MountService( 2127): externalstorage_lock_state =
D/VoldCmdListener( 4249): volume mount /mnt/extSdCard
I/Vold ( 4249): /dev/block/vold/179:17 being considered for volume sdcard
D/Vold ( 4249): Volume sdcard state changing 1 (Idle-Unmounted) -> 3 (Checking)
I/MountService( 2127): onEvent:: raw= 605 Volume sdcard /mnt/extSdCard state changed from 1 (Idle-Unmounted) to 3 (Checking) cooked = 605 Volume sdcard /mnt/extSdCard state changed from 1 (Idle-Unmounted) to 3 (Checking)
I/MountService( 2127): updating volume state checking
D/MountService( 2127): updatePublicVolumeState :: path = /mnt/extSdCard, state = checking
D/MountService( 2127): volume state changed for /mnt/extSdCard (unmounted -> checking)
D/Vold ( 4249): Detected exFAT file system.
I/MountService( 2127): notifyVolumeStateChanged:: path = /mnt/extSdCard,old = unmounted,new = checking
D/MountService( 2127): sendStorageIntent Intent { act=android.intent.action.MEDIA_CHECKING dat=file:///mnt/extSdCard (has extras) }
D/MtpService( 2366): onStorageStateChanged /mnt/extSdCard unmounted -> checking
I/StorageNotification( 2251): Media {/mnt/extSdCard} state changed from {unmounted} -> {checking}
D/STATUSBAR-NotificationService( 2127): cancelNotification - pkg:XXX.XXXXXXX.XXXXXXXX, id:1628873367, tag:null
D/STATUSBAR-NotificationService( 2127): updateLightsLocked() : Turn off notification light
D/KeyguardViewMediator( 2127): setHidden false
D/ApplicationPolicy( 2127): isStatusBarNotificationAllowed: packageName = com.android.systemui
D/ApplicationPolicy( 2127): isStatusBarNotificationAllowed: packageName = com.android.systemui
D/StorageNotification( 2251): setMediaStorageNotification : notify id = 1628873367, path = /mnt/extSdCard, title = A preparar cartão SD...
D/STATUSBAR-NotificationService( 2127): enqueueNotificationInternal - pkg:XXX.XXXXXXX.XXXXXXXX, id:1628873367, tag:null
D/STATUSBAR-NotificationService( 2127): Noti Alert - mSystemReady:true, AlertEnabled:true
D/STATUSBAR-NotificationService( 2127): enqueueNotificationInternal - pkg:XXX.XXXXXXX.XXXXXXXX, id:17301675, tag:null
E/NotificationService( 2127): Ignoring notification with icon==0: Notification(contentView=null vibrate=null,sound=null,defaults=0x0,flags=0x8)
D/STATUSBAR-NotificationService( 2127): Noti Alert - mSystemReady:true, AlertEnabled:true
I//system/bin/fsck.exfat( 4249): fsck.exfat 1.1.0
D/KeyguardViewMediator( 2127): setHidden false
D/KeyguardViewMediator( 2127): setHidden false
D/KeyguardViewMediator( 2127): setHidden false
W/PowerManagerService( 2127): Timer 0x7->0x3|0x0
I/PowerManagerService( 2127): Ulight 0x7->0x3|0x0
D/lights ( 2127): button : 2 +
D/lights ( 2127): button : 2 -
D/PowerManagerService( 2127): setLightBrightness : mButtonLight : 0
D/PowerManagerService( 2127): setTimeoutLocked::SmartSleep : after19500
D/STATUSBAR-NotificationService( 2127): enqueueNotificationInternal - pkg:XXX.XXX.XXXXXXXX.XXXX, id:2, tag:null
D/STATUSBAR-NotificationService( 2127): Noti Alert - mSystemReady:true, AlertEnabled:true
D/KeyguardViewMediator( 2127): setHidden false
D/KeyguardViewMediator( 2127): setHidden false
F/libc ( 8945): Fatal signal 11 (SIGSEGV) at 0x00000008 (code=1)
I/DEBUG ( 1901): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
I/DEBUG ( 1901): Build fingerprint: 'samsung/m0xx/m0:4.0.4/IMM76D/I9300XXBLG8:user/release-keys'
I/DEBUG ( 1901): pid: 8945, tid: 8945 >>> /system/bin/fsck.exfat <<<
I/DEBUG ( 1901): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 00000008
I/DEBUG ( 1901): r0 400aa1b8 r1 00000000 r2 00000000 r3 400a7460
I/DEBUG ( 1901): r4 400aa1b8 r5 400901ec r6 400a96a0 r7 00000000
I/DEBUG ( 1901): r8 014d98d0 r9 00000008 10 ffffffd0 fp 00000001
I/DEBUG ( 1901): ip 014d18d0 sp be94b878 lr ffffffd4 pc 4008c9a6 cpsr 40000030
I/DEBUG ( 1901): d0 3d184240309b4df7 d1 0000000000000000
I/DEBUG ( 1901): d2 0000000000000000 d3 0000000000000000
I/DEBUG ( 1901): d4 0000000000000000 d5 0000000000000000
I/DEBUG ( 1901): d6 0000000000000000 d7 3d24b3bc00000000
I/DEBUG ( 1901): d8 0000000000000000 d9 0000000000000000
I/DEBUG ( 1901): d10 0000000000000000 d11 0000000000000000
I/DEBUG ( 1901): d12 0000000000000000 d13 0000000000000000
I/DEBUG ( 1901): d14 0000000000000000 d15 0000000000000000
I/DEBUG ( 1901): d16 41ce9259de341893 d17 3f50624dd2f1a9fc
I/DEBUG ( 1901): d18 41c84da6fb800000 d19 0000000000000000
I/DEBUG ( 1901): d20 0000000000000000 d21 0000000000000000
I/DEBUG ( 1901): d22 0000000000000000 d23 0000000000000000
I/DEBUG ( 1901): d24 0000000000000000 d25 0000000000000000
I/DEBUG ( 1901): d26 0000000000000000 d27 0000000000000000
I/DEBUG ( 1901): d28 0000000000000000 d29 0000000000000000
I/DEBUG ( 1901): d30 0000000000000000 d31 0000000000000000
I/DEBUG ( 1901): scr 00000010
I/DEBUG ( 1901):
I/DEBUG ( 1901): #00 pc 0000c9a6 /system/lib/libexfat_utils.so (buf_getblk)
I/DEBUG ( 1901): #01 pc 000077c8 /system/lib/libexfat_utils.so (itr_get_next_dentry)
I/DEBUG ( 1901): #02 pc 0000900e /system/lib/libexfat_utils.so (exfat_check_dir_internal)
I/DEBUG ( 1901): #03 pc 000094e2 /system/lib/libexfat_utils.so (exfat_check_dir_internal)
I/DEBUG ( 1901): #04 pc 000095a0 /system/lib/libexfat_utils.so (exfat_check_dir)
I/DEBUG ( 1901): #05 pc 00009694 /system/lib/libexfat_utils.so (fs_check)
I/DEBUG ( 1901): #06 pc 0000ac2c /system/lib/libexfat_utils.so (ffsCheckVol)
I/DEBUG ( 1901): #07 pc 0000bff0 /system/lib/libexfat_utils.so (FsCheckVol)
I/DEBUG ( 1901):
I/DEBUG ( 1901): code around pc:
I/DEBUG ( 1901): 4008c984 f8df6821 6019e084 68626820 f8556042 !h.....` hbhB`U.
I/DEBUG ( 1901): 4008c994 6801000a 60216060 605c6803 68e26004 ...h``!`.h\`.`.h
I/DEBUG ( 1901): 4008c9a4 609168a1 68a32100 60d868e0 48176872 .h.`.!.h.h.`rh.H
I/DEBUG ( 1901): 4008c9b4 8014f8c4 61a16122 68004478 f300fa28 ...."a.axD.h(...
I/DEBUG ( 1901): 4008c9c4 200ef855 0c3ff003 134ceb02 60e36899 U.. ..?...L..h.`
I/DEBUG ( 1901):
I/DEBUG ( 1901): code around lr:
I/DEBUG ( 1901): ffffffb4 ffffffff ffffffff ffffffff ffffffff ................
I/DEBUG ( 1901): ffffffc4 ffffffff ffffffff ffffffff ffffffff ................
I/DEBUG ( 1901): ffffffd4 ffffffff ffffffff ffffffff ffffffff ................
I/DEBUG ( 1901): ffffffe4 ffffffff ffffffff ffffffff ffffffff ................
I/DEBUG ( 1901):
I/DEBUG ( 1901): stack:
I/DEBUG ( 1901): be94b838 00000100
I/DEBUG ( 1901): be94b83c 400a96a0
I/DEBUG ( 1901): be94b840 403d1f08
I/DEBUG ( 1901): be94b844 00005cf7
I/DEBUG ( 1901): be94b848 be94b954 [stack]
I/DEBUG ( 1901): be94b84c 00000a25
I/DEBUG ( 1901): be94b850 00000000
I/DEBUG ( 1901): be94b854 00005cfc
I/DEBUG ( 1901): be94b858 00000001
I/DEBUG ( 1901): be94b85c 400870c3 /system/lib/libexfat_utils.so
I/DEBUG ( 1901): be94b860 be94b878 [stack]
I/DEBUG ( 1901): be94b864 400a96a0
I/DEBUG ( 1901): be94b868 403d1ee8
I/DEBUG ( 1901): be94b86c 00016a97
I/DEBUG ( 1901): be94b870 df0027ad
I/DEBUG ( 1901): be94b874 00000000
I/DEBUG ( 1901): #00 be94b878 be94b93c [stack]
I/DEBUG ( 1901): be94b87c 400a96a0
I/DEBUG ( 1901): be94b880 00000003
I/DEBUG ( 1901): be94b884 00000000
I/DEBUG ( 1901): be94b888 403d1f88
I/DEBUG ( 1901): be94b88c be94b93c [stack]
I/DEBUG ( 1901): be94b890 00005d00
I/DEBUG ( 1901): be94b894 400877cd /system/lib/libexfat_utils.so
I/DEBUG ( 1901): #01 be94b898 400a96a0
I/DEBUG ( 1901): be94b89c 00000001
I/DEBUG ( 1901): be94b8a0 00000003
I/DEBUG ( 1901): be94b8a4 40089013 /system/lib/libexfat_utils.so
I/DEBUG ( 1901): !@dumpstate -k -t -n -z -d -o /data/log/dumpstate_app_native -m 8945
I/BootReceiver( 2127): Copying /data/tombstones/tombstone_01 to DropBox (SYSTEM_TOMBSTONE)
I/dumpstate( 8952): begin
I/CrashReportBroadcastReceiver( 7291): New report detected, starting reporting service
I/CrashReporterServiceDelegate( 7291): Running task for: SystemTombstone 10 reports (1 per task)
W/AlarmManager( 2127): FACTORY_ON= 0
E/AmazonAppstore.Applicationhelper( 7291): Received null package name.
D/CrashReporterServiceDelegate( 7291): Processed 1 SystemTombstone report(s)
D/CrashReporterServiceDelegate( 7291): 9 SystemTombstone report(s) remaining
D/CrashReporterServiceDelegate( 7291): Processed 0 SystemTombstone report(s)
D/CrashReporterServiceDelegate( 7291): No reports remaining to process for SystemTombstone, completing task
So it would seem that for now, if you're using the stock ROM, exfat formatting is broken.
