MuseScore 1.3 doesn't open on Win7

Hi, I've been using MuseScore on OSX without problems, now I wanted to install it on my new Windows 7 PC (64bit).

The problem is, that when I try to open it after installing, nothing happens. In Processes, mscore.exe is running, but there is no window.
Same thing with the MSI package and 1.2. The portable package did start once, I then changed the start screen to "continue last session" and closed it and then it won't open again.

I'm assuming this is something on my system preventing the window to show, but I have no idea what it could be. I've reinstalled it severel times and rebooted my PC. Weird thing is that the portable version worked once and then didn't anymore.

I would appreciate any help. :)
Rolf

p.s.
I just downloaded the last nightly build (2013-12-19-1507-f8187c9) which seems to work. I've opened and closed it severel times, set the start screen to "continue last session" and it still works (I think that wasn't really the problem anyway). Have to go now, will try more later.

edit:
I just noticed that Wacom tablets might have incompabilities. I didn't have my tablet connected, but the drivers are probably running somewhere. I will try to deactivate the drivers later when I get home to see if that was the issue.