I've just been given a standard Touch Diamond and I seem to be having an issue with it when I've left it idle for a while.
The issue primarily occurs over night and when I come to the phone in the morning input my pin it just freezes with "Password" in the top corner and a blank (black - my wallpaper) screen.
I have additionally installed applications above what is shipped with the phone. Active Sync is set to manual over night and the settings allowing the phone to "sleep" on battery and charge are turned off (I just left the "turn backlight" settings on for obvious reasons).
I was going to chalk it up to the length of time the phone was idle (due to it been about 8hrs), but it did it again this afternoon, as about 2hrs.
Currently my only method to "cure" the issue is to power cycle the phone, as it does respond to a long hold of the power button and gives me the power off yes / no option (obviously pressing no send me back to the blank screen)