Overclocking problem (up to 77hz)

[MrMendace]

Hi everybody, i have some problems while overclocking my monitor, let me explain;
My monitor is a "SAMSUNG SyncMaster P2050" comes with a standard R/R of 60hz and he can easily overclocket up to 77hz (My actual refresh rate) but when this happens, for example at 86hz, my monitor shows up a message "Not optimum mode... 1060x900 60Hz" at the same time i still see, it just alert me to go back to the standard R/R, but at the same time i can use it, anyway it comes black after 20 seconds and i need to go back to 77hz.
The gpu and the monitor comunicate from a normal HDMI cable, male to GPU then DV-I adapted to the monitor, i have already removed all latency blocks, but nothing....
DESPERADE, please someone if you knows just give me a tip!!!

[ToastyX]

Samsung monitors usually don't allow more than 77 Hz.