It takes 20 or 30 seconds to open a window or to start a program like gedit.
Working with the programs seems to be normal - once the the window is open. But opening another (sub-)window takes very long...
And there is another curious problem: Sometimes all windows comes in front - one after the other - very quickly. So the desktop "blinks". I can stop it by minimize the windows.
I think, I have this problem since I installed the nc10 repository, but I'm not sure about that.
Thanks for helping me!