It's my datapath at home, that going from work where I must send Full HD 60HZ, at work another one it 3840*2160 @ 25hz and NEC PA272B is my working screen with presets etc (at work I got 30 inch HP with 2560*1600 also 60HZ). And why its not compatible if they multiples of each other.

All worked perfectly with my old one catalyst server based on 10.6.8 with gtx285 with the same resolution with crushes but it will be about 1-2 time in a few month. So I think output resolution is not a cause of crushes and can't load my video cards for 100%.