I've tried a few of the Froyo ROMS and they all seem to have the same problem on my SF.
Quite often when I plug in the USB cable from my PC I get no notification at all, nothing, although it starts to charge OK.
I've searched the forum and found a few other people have this issue, but no real cures for it. All works fine on 2.1 BTW, so not cable/PC etc.
Anybody got a fix for this, please? It's driving me nuts!