That it works ok from a guest account tells me that you have a corruption issue with either a driver (in the mac world they're called extensions) or a preference file... though it could possibly be a font or some other file.
In any event the solution is to create a new master user account. Transfer only your essential files (manually reset your personal preferences and network settings, you don't want to import the corrupt file).
Once everything is working to your satisfaction you can compress and store (make an image or zip file) the old account, or delete it it.
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