Um... that's a bit odd... I doubt the monitor is actually capable of displaying over 60Hz so it's wierd that selecting the higher one would fix it. No it won't cause any damage, it shouldn't do anything.
Actually, well this is all wierd to me but anyway:http://www.viewsonic.pt/support/lcddisplays/va712b/#specs
Video Input: Frequency fh:30~82kHz, fv:50~85Hz