PokerStars had a client update today that broke Zoom.
My PokerStars.EU client updated to PokerStars 6 (build 6535 of the PokerStars client)
If that doesn't resolve it, please close your Stars client and your HM and replace the file c:\programme\rvg software\holdemmanager\blitz.dll with this one: https://dl.dropbox.com/u/13215305/Blitz.dll
This will only work if you used the default Holdemmanager Installation folder. If you used a different folder during the original installation you have to replace the file in your custom installation folder.