Macbook Pro, was having trouble with cheap knock off MDP to DVI convertor with crappy 19" television as second monitor. Tested with same adapter and 20" LCD monitor, still froze up. Bought Apple adapter, using 20" Dell monitor at new job, and problem went away, for a day and a half.
I have tried all the suggestions listed, and some seem to help, but it feels random. My experience was that booting up with Bluetooth turned off, then turning it on and pairing my wireless keyboard and Magic Touchpad yielded a day of heavy use with no lock-ups. This morning I turned it on and just let it re-connect, and it went 6 hours but then froze up, just as before. I will contact Apple support again tomorrow, who have been extremely helpful thus far.
As an aside, with no external monitor plugged in, using no external peripherals, I have NEVER had a lockup. I have noticed a repeating issue where the monitor will dim, the backlight on the keyboard will go out, until I hit another key or touch the touchpad. It will happen even seconds after my last input, not seeming to have anything to do with sleep or screen saver. Anyone else notice this in combination with this dis-heartening lockup?