The ImageShack virus hoax has been causing a lot of problems lately. It is pretty much the same as the old scam of setting a paper bag of dog poop on fire on a front porch and ringing the doorbell.
Clicking anywhere on the "Alert" pop-up box gets you in trouble, just like the stomping on the bag of poop.
If that scam gets you in trouble, you are way too vulnerable. Higher protection levels are needed. Norton 360 will block suspicious behavior by a Web site. Firefox will block the annoying pop-ups.
Never click on pop-ups you don't trust 100%.