Windows 7: My guess something is wrong

This is what i see after browsing 9gag for 1 hour.

I'm using firefox 7.01 and this happens frequently.

What plugins do you have in play? I just browsed there for a bit and noticed nothing specifically wrong with the site.
In fact ff never passed 300k the entire time I was loading pages like mad trying to make it blow up.

That looks like a classic Firefox memory leak. Can be caused by a corrupt installation.
I suggest uninstalling Firefox (you can keep your settings), restarting the computer, and reinstalling a fresh copy from a download.

I have this same problem with FireFox... it isn't due to plugins or any specific websites, it just goes up and up and up eventually into the 1,000,000k mark and then freezes altogether until I have to close the processor thread out or even restart the system to get it back. I only use Adblock plus, java and a custom theme as far as addons are concerned (all of which are kept up to date, and which I had uninstalled to see if they were the problem - didn't change anything). Some systems apparently just don't like FireFox and we either put up with it, or we switch to Chrome (but for me, Chrome also hogs memory just as bad and sometimes even worse - but without the freezes and crashes). Also, it doesn't matter how many times you try to uninstall/reinstall... seems to happen no matter what you do or what you have/don't have in way of addons. This isn't a new problem... it's always been a problem for me, ever since I started using FF in 2006 (and with a different computer, too).

Could this be an issue limited to 64-bit Windows?

Mine is 32-bit and I've never seen this happen since at least FF3.5...

Not likely, my old system that this problem also prevailed with was a x32bit Win XP.

I think this happened due to some kind of issue with the Aero system of firefox.
I switched to a new theme i liked, and the issue is gone.

A memory leak can occur anytime a software program is changed, updated, or added on to. The issue isn't with Firefox the Program per se, but to the individual Firefox installation. Firefox (or Chrome) installs and runs just fine on millions of computers, but because it is one of those programs that is constantly updated, and allows many user configurations there is always the possibility that the installation can become corrupted. That's when you get the leak.

And it makes sense that a theme add on would do it.

Just keep in mind that when you observe the behavior (with any program - not just Firefox) that the first course of action should be re-installation - or if available in the installation package, a repair install. Or as in your case - remove the offending module.

More!: Memory leak - Wikipedia, the free encyclopedia