[2K3] SPRITE LIMIT?

Sorcerer is far from the end of the alphabet. I find it hard to believe you have 269 enemy images and none of them have names that start with letters after S. I suspect it's also cutting off some of your custom images, and the limit is probably 255.

However, try this. Make an enemy that uses the last graphic in the list. Then add a new graphic, so that the last one gets bumped off the list. And then check to see if the enemy you made still works. If so, try something else: add a new monster graphic with a filename that starts with the letter z, and check to see if it shows up in the list.

It's very possible that even though it's not listing the file in the database, it's still able to use it in the game. You would just need to start giving all your new enemy graphics filenames that start with underscores from now on, to make sure anything new you add isn't instantly pushed off the end of the list by old stuff.

If there is a limit I haven't hit it yet. One of my projects has become a dumping ground of resources and has nearly 3500 monsters in its folder.

If you had a restore/data loss on the computer I would assume that it is a computer problem (most likely hard drive). If you don't have a backup on a separate hard drive I'd try taking your current project and copying it onto another hard drive, adding monsters and checking to see if it still has the same issue.

As a quick test, try downloading the RPG Maker 2009 Ultimate (an addon for 2k3) from http://cherrytree.at/ultimate and test with it (it uses a different method to enumerate the files, because it also supports subfolders).