Just figured out, that the problem is gone with the 2.6.22 kernel image from gutsy repo.
So the problem is there in feisty with 2.6.20-15: linux-image-2.6.20-15-generic 2.6.20-15.27
and no problems with 2.6.22-1 from gutsy: linux-image-2.6.22-1-generic 2.6.22-1.3
Just figured out, that the problem is gone with the 2.6.22 kernel image from gutsy repo.
So the problem is there in feisty with 2.6.20-15: 2.6.20- 15-generic 2.6.20-15.27
linux-image-
and no problems with 2.6.22-1 from gutsy: 2.6.22- 1-generic 2.6.22-1.3
linux-image-