I have built a new system: P8Z77-I motherboard, Intel i5 3570K with Intel HD 4000 Graphics CPU, 16Gb RAM. Ubuntu 12.04 was installed without internet connection, now it's connected but I haven't run updates.

I installed ubuntu just fine but once in a while it hangs. Nothing will make it turn off unless I disconnect PSU. This is not something I like to do therefore I was wondering if someone might have any idea of what the problem is. Things that occurred to me: intel driver doesn't support 4000HD graphics, kernel doesn't support cpu or motherboard, or an hardware problem like PSU doesn't provide enough wattage for motherboard.

Any suggestions?