If you were one of the unlucky risk takers who ran into issues with the NemoPlayer, then here are some steps which should get your gallery fixed without having to completely factory reset your Droid.
Instructions for non-rooted users…
1. Uninstall NemoPlayer.
2. Mount your Droid to your computer.
3. Copy every single file on your SD card over to a folder on your computer.
4. Delete the “Android” folder.
5. Unmount your Droid and go into Settings>SD Card>Unmount SD Card>Format SD Card.
6. When that finishes, mount your Droid to your PC again.
7. Copy back over all of your SD card files to your Droid.
8. Unmount your Droid.
9. Done. Fixed.
Instructions for rooted users…
1. Restore a backup or flash a new ROM.
Thanks to @jamerson90 for the fix!