Windows Really high CPU usage from Firefox?

Hi, I've just noticed recently tht when I have Firefox open with a few tabs, esp. those with lots of Flash & gifs etc. my CPU usage is very high (basically 100%). I have AV and XP SP2 and didn't really notice this before SP2 (I only have a Sempron2400 at the mo but surely that should cope with internet browsing ).
Can anyone shed any light on this - is it SP2, Firefox or perhaps some Spyware ive missed?

 

It's probably down to flash and animated GIFs, I've notice the same thing when there's a lot of movement going on.

 

some ads on ign.com just totally lock firefox up on my fiancee's box - and the same ads only make my box stutter for a split second - main differences in our rigs are

512 vs. 1024 mb ram
xp 1800+ vs. xp 3000+

boths running FF 0.9.3

 

It's a change in FF 1.0PR compared to the lower versions. I found with my old system (Duron 850, 98SE, 256Mb RAM) I couldn't open IE6 properly with IEView if I had more than 3 tabs open in FF, even plain simple pages. Seems better now with Sempron 2600+, XP, 512Mb RAM.

Been a lot of complaints on the higher memory footprint in the Moz forums.

 

I'd say it was a quite significant problem then. The high CPU usage doesn't really go with the whole compact, high speed browsing. They should perhaps allow limiting the amount of CPU\memory used to render flash and animated images, I'm fed up with adverts using all my CPU cycles!