If I right click on the desktop or a folder I get the usual 'right click' dialogue. Files are a different matter. Notepad is OK, but images and audio files do a brief 'flash' but no dialogue. Sometimes double right clicking brings it up, but not always.
It was working correctly last week, but not yesterday or today. Other than that I can't say exactly when it started. All the searches I have made on the web do not cover this error.