http://social.technet.microsoft.com/Forums/en-US/outlook/thread/0b9942d3-78df-4421-9ebd-3d7df940f076/

http://support.microsoft.com/default.aspx?scid=kb;EN-US;970920

Outlook Safe Mode disables all plugins, which are the most common causes of problems.

In Outlook 2010 on Windows 7, you just hold down the control key when clicking the icon to start Outlook.

In older (any) versions of Windows, you can run this command in the Run dialog box:

outlook.exe /safe

To determine which Outlook plugin is causing a problem:

1. Disable all plugins
2. Re-enable plugins one at a time
   • You probably want to enable the anti-virus plugin first

Disable all plugins:

1. File → Options → Add-in → Go (button next to “Manage: Com-in Add”
2. If there are any add-ins, clear the checkbox to disable them
3. Close Outlook, wait a few seconds, then restart it

Enable plugins one at a time while testing for problems:

• File → Options → Add-in → Go (button next to “Manage: Com-in Add”
• Enable one plugin (check the box) at a time
• Restart Outlook between tests
• Repeat the above procedure for each plugin you want to re-enable
• Once the problem reappears, you have found which add-in is the cause
• Leave the problem add-in disabled and either live without it or pursue a fix