Matej, can you please test against Gutsy or Hardy to see if the issue still exists?
Everyone else who is reporting having the "same" problem, I think you are probably experiencing separate issues, despite having similar symptoms (if the symptoms aren't 100% the same as the original poster, they're most likely unrelated); please test against Hardy and if the issue still exists for you, report new bugs on them, attaching your /var/log/Xorg.0.log, /etc/X11/xorg.conf, and the output of lspci -vvnn.
Matej, can you please test against Gutsy or Hardy to see if the issue still exists?
Everyone else who is reporting having the "same" problem, I think you are probably experiencing separate issues, despite having similar symptoms (if the symptoms aren't 100% the same as the original poster, they're most likely unrelated); please test against Hardy and if the issue still exists for you, report new bugs on them, attaching your /var/log/ Xorg.0. log, /etc/X11/xorg.conf, and the output of lspci -vvnn.