!!!EMERGENCY!!!

[Guest]

if i change 1 of the tile sheet to a different one (because 5 are the same) and try to open it in the map editor it gives me this error
error#53
there was an error opening thins program
description:error finding file C:\blah\blah\blah\Tiles6.bmp
when i click ok it closes the client.
(same happens when i change the item shheet to a paperdolling one) I can't do paperdoll!! or make anything look better!! what do i do!!!????