Can't open Logic Pro after having installed Mountain Lion

After having installed Mountain Lion I can't find Logic Pro (the latest version) back in my programs. I do still find all of my sessions. Trying to open a session a "Basic Content Download" starts. Just before the end of the download the computer asks for my password. After I've typed it and pressed enter the download stops.

This means I can't open any of my sessions.

What should I do?

Thanks for any advice.