Yeah, what Bitt said. "Fault" doesn't mean faulty in this case. It just means that there was a ram<->disk swap happening, which happens all the time on computers, even when things are working normally.
So: run fewer programs or buy more RAM.
He's got the maximum possible memory for a 32-bit system, and this is an overnight backup (i.e., not a lot of other programs running).
A backup program should not cause a machine to run out of RAM and slow to a halt. Something else is going wrong here, something OS-related or software-related.
Sometimes I've seen AV programs get into race conditions with backup programs.