Files open in 2010 not 2011, why?

All of a sudden, when I click a 2011 file in Windows Explorer, it now tries to open in 2010, I then get the message that it can't be opened because its a newer file. I know this, as I created it in 2011.

This started happening on Tuesday, and is fairly annoying.

Has this happened to anyone else, and how do I rectify the problem?

Thanks in advance.

Phil.

SolidworksAdministration