Unity desktop on Ubuntu 12.04. Three GTX-670 cards connected with SLI bridge.
Three monitors.
Using Basemosaic.
Hard freezeup occurs on average after one week of operation. Sometimes lasts up to two weeks, sometimes happens after a couple of days, or even a couple of hours.
CPU noted going to 100 percent during these events.
System mostly used for web, email, desktop processing, no gaming.