Hi,

Could be a lot of things, trojan, malware. I had the same, crashing during rendering, memory problems (not only with maya).
A few weeks after this started my ISP disconnected me from the internet saying i was part of a botnet and they allowed me only to a few websites through their proxyserver. I had a trojan in my MBR and after a fdisk /mbr from DOS it was still there.
Try to use Cureit, it's free and very good, you can download it here. It removed the trojan from MBR while i was in windows. After the initial check don't forget to scan all your drives.