Just for info, as it might benefit others with MD's running integrated NVidia cards.
I own 2 Asus T3 barebone pc's running as MD's: http://www.newegg.com/Product/Product.aspx?Item=N82E16856110061
. It runs an integrated NVidia GeForce 6150 video card.
I experienced a lot of hardlocks on these machines, as it turns out video related. Mostly when watching TV (mythtv) it could suddenly freeze, requiring a hard reboot. Most profoundly it freezed when watching LiveTV and using the LinuxMCE menu's, I use UI2 overlay.
Last week I upgraded the NVidia drivers on the MD's to 180.51 as per wiki: http://wiki.linuxmce.org/index.php/Display_Drivers#NVidia_Chipsets
. Since then I have not encountered anymore hardlocks on my MD's.
Maybe this might help someone with similar problems...