I regularly run a registry cleaner. Lately I have been getting one particular error constantly reappearing that does not always get cleaned the first time around. I do not know what the key is for but it is in the "File Association" section. Could this be related ?

File Associations(1 Problems found)
Section: HKEY_CLASSES_ROOT\Application.Reference\shellex\ContextMenuHandlers{90AA3A4E-1CBA-4233-B8BB-535773D48449}
Reason : This registry key points to the missing CLSID {90AA3A4E-1CBA-4233-B8BB-535773D48449}