I tried the official debian-wheezy-live-a2-i386-lxde-desktop.img now. But the problem is still the same: it hangs up with a black and white pixeled screen (just like heavy snowfall). In failsafe mode it's the same. Boot option vga=0 has no effect too. Because I can't see anything on the screen I can't read any messages nor have a look at a log file. Oliver