Another cause identified as DivX shell extension:
http://forums.divx.com/viewtopic.php?to ... 1&forum=24
Workaround:
Eliminate the context-menu handler from the registry, or disable it temporarily using ShellExView tool.
Eliminate the context-menu handler
Click Start, Run and type REGEDIT. Navigate to:
[HKEY_CLASSES_ROOT\*\shellex\ContextMenuHandlers\EncodeDivXExt]
Backup the key to a REG file, and delete EncodeDivXExt key
Close Registry Editor and restart Windows
-or-
Disable the DivX context-menu handler using ShellExView tool
In ShellExView, the entry might read as EncodeDivXExt Module
How do I use DivX software on Windows XP SP2?
http://forum.aumha.org/viewtopic.php?t=7264