Ok that's a strange one. Did you change resolutions or anything like that? Some monitors run better with different combos of resolution and refresh rates. Have you hooked another monitor up and tried running it at 60 to see if everything works ok? If so, then I would say it's something with the monitor.
I ran it on my friend's 42" with no problem. I had to adjust the screen and stuff for my 19". Other than that. Nothing was changed. It automatically adjusted on the big t.v. Putting it to 60. The whole screen turns blurry with white discolorization. (Hope that's a word) Putting it on 70Hz. It's as crisp as ever.
I screwed up one once by unhooking it while the monitor was powered up. the computer was off. but it never was right after that. the picture was all pink but I could still see everything, it was just colored pink. gay video card? LOL