Steps

1. Execute > regedit > Right clic > Execute as Administrator
2. Go to the key "HKEY_CLASSES_ROOT\*\shellex\ContextMenuHandlers"
3. In this key, all shell extensions are listed which work with all files. The * is a real *, it does not mean "any keys" here!
4. Choose "Registry" > "export registry", so you can revert your changes later. Choose to export only the selected branch
5. Now delete them one after the other, and then try each time a right click on your desktop or Ctrl+C, to check if it works again. This way you should find the defective extension
6. When you have found it, you need to double click the .reg-file created above to restore all shell extensions, and then delete only the malfunctioning extension
7. /!\ If the error happens with directories or with virtual folder, you may have to repeat this with the keys:
8. HKEY_CLASSES_ROOT\Directory\shellex\ContextMenuHandlers
9. HKEY_CLASSES_ROOT\Folder\shellex\ContextMenuHandlers