Just adding to the known information.
I have the same issue with my GA-Z87X-UD3H hack, freezing randomly and becoming completely unresponsive unless force rebooted. The screen seems to freeze, but the computer continues to run, fans and everything.
I seem to notice the problem more when using audio and USB, and sometimes on reboot I get a kernel panic. Unplugging the USB drive generally works in this case. The kernel panic does not seem to have a specific issue with any kext though. Using Chimera 2.2.1 seems to have lessened the freezes from 3.0, but they still occur. I have monitored temperatures, but nothing seems to be too out of hand (at medium stress the system runs at 55C).
Reinstalling the os has not worked, and the issue comes up in all the current versions of mavericks. I have tried bumping the memory voltage as well, with no success. Updating to the latest bios (F9) has been a bit of a challenge though, as was not able to use Q-Flash as I did with previous updates.
This issue was really bad with Chimera 3.0, and it interfered with my schoolwork, much of which has to do with movie/film making since I am taking a video production class. Chimera 2.2.1 is better, but the issue is still an annoyance. If this info sparks anyone's creative mind, please reply with any ideas, and I would be happy to test them out.
devdev001
Edit 1: Seems like it was GenericUSBXHCI.kext... got rid of it, usb 3.0 works and no freezes so far. I don't know why it would be this as I had no issues under 10.8.5, 10.9, or 10.9.1, but then started under 10.9.2 and even on rollback are not fixed.