New Kubuntu 12.10 on new hardware locking up

I have installed Kubuntu 12.10 on a new computer. Every few hours of work, the system locks up. The keyboard and mouse are unresponsive, and the screen does not change even if there are screen elements that should change (such as a countdown timer or the system clock). I cannot use Ctrl-Alt-F* to get to a terminal. The hard drive light flickers briefly once every 10-15 seconds, this is a much slower pace then is observed when the system is functioning properly.

The applications running at the time of lockup include: Skype, RSIbreak, Zim, Anki, Firefox, Konsole with an active SSH session, apache2, mysqld, and of course KDE. The issue has occurred with 2 different keyboards, but I have not tried a different mouse yet. As these are the tools needed for work, I cannot simply run for a few hours with them disabled to see if any are the 'guilty party'. The lockup occurs both while I am actively typing on something, or if I have stepped away for a few minutes.

• Gigabyte F2A55M-HD2
• GeForce 210
• AMD processor, 4 GiB memory, 1 TB hard drive, 500W power supply

More detailed hwinfo can be found here.

I plan on running memtest overnight. What else should I check, and how might I get a log of the problem?

EDIT: The system just locked up again with only Firefox, Chrome, Konsole and KDE running. Here is the syslog.