You can have your DROID rebuild the thumbnails, no big deal. Unfortunately, I can't remember where those files are stored at the moment. Once you delete the thumbnails, your DROID will recreate new ones ... that should correct the issue.
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UPDATE: Connect your DROID up to the PC/Mac and explore the sdcard. There is a folder called DCIM ... that's where all of the pics are kept, as well as the thumbnails. There should be at least 1 ".thumbnails" folder in there. Delete all of them, unmount the sdcard and go back into the Gallery. The DROID should rebuild the proper thumbnails.
(You could save the thumbnails folders to your PC, if that would make you feel more comfortable.)