Edit :- I think this might be an easier way to fix the issue :-
Download ShellExView (from nirsoft.net) and run it. It will scan the registry for all the shell extensions. Once the scan is over and the list is displayed, you need to spot the context menu handlers. Sort the results using "Type", so that the context menu handlers are displayed together.
Disable non-Microsoft context menu handlers *one-by-one* and verify if the problem is solved. If disabling one does not solve the problem, undo the disabled item and disable the next non-Microsoft handler. Do the same until the problem is solved and finally identify the culprit. Scroll right to see the Company Name column in ShellExView.
ShellExView :-
http://www.nirsoft.net/utils/shexview.html