So nobody is willing to help me?
I think I've found what's causing the problem - it's garbled EDID (see -> http://www.nvnews.net/vbulletin/showthread.php?t=81707
However, I have some trouble using alaric's solution:
1) In order to be able to use 1.0.7676 nvidia drivers I need to compile 2.6.15 kernel, but the compilation process of 22.214.171.124 (same with 126.96.36.199) kernel ends with -> http://pastebin.ca/379508
. I also can not install the legacy driver from the repositories, because nvidia driver installer screwed my system and drivers from repositories can no longer find wfb module.
2) The custom EDID made by alaric doesn't work for me, because my monitor is not "IIyama Vision Master Pro 17" and I don't have enough experience to make my own custom EDID.