Heat issues, possibly? I just had a scare with a laptop that locked up, lost its backlight temporarily, and couldn't boot because its internal fan had gotten stuck and it was overheating...
Sounds like a possibility, but I didn't notice much dust in the machine when I opened it up. The PS fan is so tiny, I think it might be a 20-40 mm. If it is a heat issue, there isn't much room at all to add a secondary fan. This is the problem with these machines I've noticed, cheap price but not much thought on possible adding onto them.