You should say which version of Office's Outlook you have. This error might be caused by a recent update. Try a Repair. T he repair for Office 2007 is in Control Panel, Add/Remove Programs, Change Office 2007, Repair.

i'm sorry, i do have outlook 2007. i have tried to do the repair before and it didn't change anything. it didnt report a problem with the repair when it was finished, but the same error popped up after i repaired and rebooted.