This might be the error you get when you try to load a character that has an item with an ID# that doesn't exist in the client bins. I can't be for sure without being at my computer.
Try deleting the affected character or if the character selection screen won't load, go into the database and delete the character from there.
In the future make sure that when you modify ID# that you don't affect items that are in character inventories and that the server and client bins match up.
Assuming that I'm correct about the error you're having of course
error 5637
