Page display gets weird while two-finger scrolling

Question

For the last few days, whenever i'm scrolling with two fingers in safari, the page's display gets very disrupted....numerous white rectangles appear and disappear quickly over the page's content, returning to normal when scrolling ceases. This happens on every page of website, about 80% of the time on any given page. Sometimes it won't do it once i've scrolled over that area once. Restarting my MBP doesn't change anything.
Yesterday, though not today, safari would only load a page if I clicked onto another application and clicked back on safari. totally bizarre.

Answer 1

nowhere in this thread has anyone suggested zapping the PRAM, which is a much more extreme measure than trashing a finder and system preference. i mean, if it doesn't work and you lose your settings, you can always take the file back out of the trash and put it back. with a pram zap, you can't go back. so, i can't see any reason for you to not trash those two prefs since that's what worked for me. as a rule, always trash prefs before zapping pram. and do a permissions check while you're at it for good measure.