video trouble

i have a four year old macbook. if i have an internet video running (netflix/hulu) with any additional tabs open (in particular another image heavy page), the tab with the video open begins to skip. i can sometimes "fix" the problem by leaving a tab with no images open while i listen to a movie, but that isn't really a "fix". the biggest problem being, that if i don't switch tabs or pause the video soon enough a grey screen scrolls down and tells me that i need to power the computer down. i worry that my computer can only handle this for so long.......any help?

Thats a Kernel Panic and means there is something very wrong, you are breaking your Air letting this continue. Take it to an Apple Service Centre, near you.