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Woah... Create a new project just to see if it has the same problem. If not, just copy your data folder over. (Unless you have custom graphics and audio, in which case copy those over too.) If so... You might need to try reparing your game.
You might want to try downloading the RMXP 1.02a (or whatever it is) update patch from enterbrain. Go to their English site, and it is the only patch. Download it and install it, and this should be fixed. At least, I think this was one of the problems fixed by the patch.