This has become a burning issue for most of Outlook 2010 users. But it's not a big deal. You may try these solutions to overcome it:
- You may try to run Scanpst.exe, which is a built-in repair tool of MS Outlook.
- You may try to run Office repair from Program Features.
- You may try to fix this by upgrading the Operating system and MS Office suite.
Try all these solutions one by one, and let me know which one worked for you.