MultiTerm 2015 won't open: please help!!!

MultiTerm 2015 standalone app won't open on my desktop nor will it open through the icon on the welcome page of Trados Studio 2015. No other versions of MultiTerm are installed. When I click on the desktop icon, it shows that it was selected but nothing else happens. It's the same in Studio 2015 when I click on the Termbase management icon on the welcome page. But the termbase is enabled in the Editor mode and I can add terms to it, so it' very strange. When I open my file, I also get an error message saying that the languages were changed (they weren't) and that I should reorganize the termbase, but I can't because I can't open the app!!!

Can someone please help me?

Thanls ahead.