50% decrease in performance after overclock??

[DioCassius]

Hi all. I've got a gts pro that i was recently trying to overclock. the memory is set to 400 default, and i went up to 430 no problem...but when i went to 435, my q3A fps dropped from about 100 to 50 at 10x7x32. i rebooted with the default memory clock, and performance returned, but not quite to normal...i got a 2 fps decrease with everything set the same. this is not a big deal, but its kind of scary that it seems i've damaged the card or something. Has anybody heard or witnessed similar situations, and is there something wrong here? thanks.