Sometimes, problems with context menus can be caused by third party programs adding shell extensions which may be corrupt or poorly written.
My suggestion would be to use something like ShellExView http://www.nirsoft.net/utils/shexview.html
The download is near the bottom of that page, but....
Take some time to read the sections on use and how to enable and or disable some shell extensions.
Run it administrator and leave the default options as they are except.....
Click the "Options" menu item and check the box to "Hide all Microsoft Extensions".
See if you can identify anything from the list that might be causing your problem.