Guitar Hero 3 LCD lag

Hi,

My specs are as follows:

OS: Windows 7 64-bit
AMD X2 4000+ (OC'ed to 2.7ghz)
ATI HD3850 256mb/256bit (Stock)
4gb DDR800 Ram
320gb WD SATA HDD
500gb External HDD
450watt PSU

26inch LG LCD TV (Primary Display)

On to the problem.

60 percent of the time playing Guitar Hero 3 (Patched to 1.31), the game the FPS drops to 15. Even changing the resolution from 720p to 1028x768 makes no difference. Before I got the LCD I played on a 17inch CRT and there was no lag whatsoever. Bioshock, Fallout 3, SF4, Mirrors Edge all play fine on max settings with a stable FPS throughout.

I tried the Video and Audio lag tool and it didn't help at all. The LCD is connected with a HMDI cable through the DVI to HDMI converter. Is there any way to get stable frames from this game since It's my primary destresser after a long haul at work lol.

I submit my humble request to the Tom's Forum Gods.

Thanks