XF86config/monitor

Hi all, I have a Samsung SyncMaster 753DF. Resolution is great, nice colors, etc, but from time to time the monitor would start making a high pitch noise. It is very annoying. I took a look at my XF86Config and saw that HorizSync is always out of range (15-72) and it should be 30-70kHz. If I change it to the correct values, it gets even worse. Any way I can fix it? Other than buying a new one of course... Help!!!