RE: Programs using a lot of memory
It's also good to backup to multiple types of media when possible like hard drives, cd, dvd's, USB sticks, etc. I also know people who use multiple backup/imaging apps just to be sure.
When's the last time you defragged your hard drive? You could run ccleaner then defrag.
Sorry, I forgot you tried the Firefox betas.
I'm about out of all the easy ideas. You could always check your memory with memtest if you wanted to. There a program called PageDefrag that defrags the page file. You could try running Firefox(safe mode) and see if there is any difference. Try disabling add-ons one at a time to see if there is a difference. I know you tried disabling the AVG scan thing. And, you could always buy more memory. NewEgg is an excellent place to buy computer parts with great service.