First make sure you have the latest XviD video codec found there
http://koepi.roeder.goe.net/xvid.shtml and make sure your Windows is updated.
Second if it continues to do this try with different software.
Third if it continues to do this.I think you have no choice but to desactivate Windows for creating and updating thumbnail.
This techniques requires to edit the registry.
Click on "Start", "Execute... " then type "regedit" and click on "OK" to reach the registry editor of Windows.
Then browse to that key:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{87D62D94-71B3-4b9a-9489-5FE6850DC73E}
Below this key,you should see one named InProcServer32 .Just delete it.
Found this hint on a French site and thanks them.You can find that hint, in french if you can understand it at
http://www.generation-nt.com/astuces-123.html
Btw they offers .reg to deactivate and reactivate that key.