Whenever people ask me about Outlook flakiness unexplained crashes and freezes, sluggish behaviour and the like ? my first recommendation is to create a brand new outlook.pst file. That sounds like a difficult job, but it isn't. Here's how you do it:
1. Shut down Outlook.
2. Go into Windows Find (Start/Find/Files or Folders, or some such), and find outlook.pst. You may have more than one, in which case you can reincarnate all of them. Remember where the file is located.
3. Right?click on outlook.pst, click Rename, and give it a new name ? say Backup 0012.pst.
4. Start Outlook. It'll bellyache and pitch a fit, but just keep clicking OK or Open ? all the defaults ? and you'll be fine.
5. When Outlook appears, it'll be fresh as the virgin snow. Welt the virgin snow in Colorado, anyway.
6. Make sure Outlook is showing folders (the way power users already have it anyway) by clicking View, and making sure Folder List is checked. Take a look at your folders list. You'll be adding a new folder, and you'll want to be able to identify it when it appears.
7. Inside Outlook, Click File, Open, Personal Folders File. Locate the old outlook.pst file ? presumably called Backup 0012.pst or some such ? in the location you noted in Step 2. Open it. The file will immediately appear in the Folders List, and it'll be called Outlook Today. This is the OLD Outlook Today folder ? not to be confused with the new, fresh Outlook Today folder, which you created back in Step 5.
8. Right?click on this old Outlook Today folder in the Folders List (make sure you don't get the fresh, untouched Outlook Today folder), pick Properties and click Advanced.
9. In the Name box, give the old folder a new name. "Backup 0012" would be appropriate. While you're sitting in this dialog box anyway, click Compact Now and give Outlook a minute or two to compact the archive file.