Outlook 2010

If your problem began on December 8 or 9 2015 and affects Outlook 2010:

In Outlook 2010, all of my options were reset to their defaults and when I change them, the changes don't stick. As soon as I close Outlook and restart it, everything is back to its default.

This is caused by installing KB3114409 - it causes Outlook to run in Safe mode, which uses the default settings. Your customizations aren't lost, they just aren't being used when Outlook is in Safe mode.

Microsoft released this update to fix the problem: December 16, 2015, update for Outlook 2010 (KB3114560). It is highly recommended that you install this update instead of uninstalling KB3114409.

Microsoft removed the update, so users who haven't installed the December updates yet won't be affected. Users who are affected should install the hotfix December 16, 2015, update for Outlook 2010 (KB3114560).

A second option is to set a registry key to disable Safe mode. If you are in a hurry, this is obviously the faster fix but you won't be able to use Safe mode in the future (for troubleshooting) until you remove the key.

To set the registry key:

1. Open the Registry editor by pressing Windows key + R. Type regedit in the Open: field. Then click Ok.
2. Browse to HKEY_LOCAL_MACHINE\Software\Microsoft\Office\14.0\Outlook\Security\
3. If any key in the path is missing, you'll need to create it. Right click on the last key, choose New, then Key and type the key name.
4. Right click on Security key and choose New, and then DWORD Value.
5. Type DisableSafeMode, and then press Enter.
6. Right-click on DisableSafeMode, and then click Modify.
7.  In the Value data box, type 1, and then click OK.
   
8. If you have 64bit Windows and 32-bit Office, also add DisableSafeMode, Value: 1 to this key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\14.0\Outlook\Security\
9. Restart Outlook or reboot the computer.

If you don't want to edit the registry, you can use this reg file: DisableSafeMode.reg DisableSafeMode.reg for Outlook 32 bit on Windows 64-bit

Video Tutorial: How to use a .reg file

Uninstall KB3114409

To uninstall updates:

1. Open Control Panel
2. Begin typing Installed Updates in the Search Control Panel field at the top right.
   
3. Click on View Installed Updates on the left
4. Begin typing KB3114409 in the Search Updates field in the top right
   
5. Select it and click Uninstall in the bar above

Outlook 2007 or 2003

The original reason this article was written in 2011 was caused by an issue with the search service. Outlook 2003 and 2007 are affected by this problem.

Solution: Repair your Office installation and run scanpst on the data file.

The problem is caused, in part, by the 'Windows Search' service. This service provides Outlook's Instant Search and Window's file search features. For a quick fix, you can stop or disable the Windows Search service.

To do this, open the Administration Tools folder in the Control panel and double click on Services. Look for Windows Search in the list. Double click it, then click Stop and Apply. You can also right-click on Windows Search and choose Stop. The next time you use Instant Search or Windows Search, the service will restart. To disable the service for a longer period, select Disable in the dropdown and click the Stop button, then Apply.

Please note: when you disable the search service, Windows File Search and Outlook's Instant Search won't work. Stop the Search service only so you can use Outlook in "normal" mode until you have time to repair it.

In Windows 7, you can type Services in the Start menu's search command or in all versions, type Services.msc in the Run command.