Problem installing with onboard video AsRock

Hello, I have problems installing Ubuntu 64. After some installations the computer at any moment hangs, freezes. Several new installations have I made, changing RAM memory, monitor, etc. It seems video freezes. I found in syslog nouveau MMIO FAULT. Could it be this? I could not install NVidia drivers, I tried nvidia 304.135 ... and it was a nightmare. Any hints for newbies? Thx...

In the Subject you mention onboard video AsRock, and in the description you are talking about Nvidia drivers and Nouveau. Which is it? If its onboard video would it not be intel graphics?