Our company still uses Outlook 2007 (Exchange 2010 server) and my boss has an issue where categories seem to generate by themselves. He'll create a calendar appointment and, when he saves it, it will randomly add categories. Plus, it will recreate deleted categories and add those to random appointments. I have tried reinstalling Office, deleting and recreating all categories and regenerating the master category list. I haven't been able to find any information about this issue and was hoping someone out there might have a solution.