@notalive: If your device wasn't jailbroken, yes. If not, just reinstall the hacks.
@ext233: Answered in the other thread, but the answer is basically the same as what I just said to @notalive
@kuoirad: Make sure you don't have any extra files that popped up in your screensavers folder, and that all of them are in the proper format.
@kaswistry: Same answer as @kuoirad. Bad files. (Or, yeah, something else messing with it, caught your latest replies, sorry
A couple of different ways to verify the format of your files would be to either check them one by one through ImageMagick 'identify' tool (not bundled, so you'll need a *nix box), or to try to print them on the Kindle via eips -f -g and check that they show up properly.
The default screensavers are backed up in linkss/backups
@grant.ben08: Can't make heads or tails of what you did, as you seem to have been mixing up a lot of different stuff. What did you install/use, and what doesn't seem to work?