I downloaded and installed iOS 4.1 today on my iPhone 3G and everything was fine until I checked my photos and noticed that there was no thumbnail for the Camera Roll and when I tapped the Camera Roll, instead of the usual thumbnails there was a nasty, black, jagged square on the screen. If I tapped the screen it would bring up the slide show and all the photos were there. Weird, and not very pretty!
I found this fix posted by ‘CharismaG4toMBP’ in this Apple Support Forum Thread, and it worked perfectly:
Download iPhone Explorer (Google that one and it’s free for Win/Mac).
Plug iPhone in and navigate to the PHOTODATA folder.
Locate these three files:
Save them to your computer. (I couldn’t figure out how do do this, so just went to the next step)
Delete them from your iPhone.
Restart your iPhone and let if boot fully.
Open ‘Photos’ and wait for the iPhone to ‘rebuild the library’.
Enjoy your thumbnails once more!
I hope this works for you too!