I'm having the same issues as some of you; my iMac completely locks up when I visit certain web sites (TechDirt, AppleInsider) and even though it's dealthy slow to get to, I can launch Activity Monitor and kill off 'Safari Web Content' which gives me enough time to close the offfending page and I'm back in business. So annoying!! I'll try to see if a flash update will help. Not too happy.
I think this may be the same thing I'm experiencing... I am curious to know if any of you that are following this will clarify if this is the same bug I'm experiencing. How will you know? When ever this type of thing happens to my 27" Core i5 iMac, I am able to unfreeze it by pressing Volume Up, Volume Down, Mute, Chang the screen brighness... anything that brings up an "overlay" dialog from Mac OS (as seen here). Does this 'work around' work for anyone else here?