I've been having an issue with Cyanogen 7.03 where it would occasionally slow down and act like something was using 100% of the processor. If music was playing, it would skip and play a short burst every half second or so. All interface elements would be unresponsive. If I hit the power button, the screen would shut off, but the tv-off style animation would play in 3 or so frames over 1-2s. After maybe 10-15s, the phone would snap out of it and go back to normal. This would happen sporadically. I could go days without seeing it and then it would happen twice in an hour. I couldn't find any information about a problem like this on various forums, but maybe my google-fu is weak.
I figured I'd just tough it out and hope it was fixed in 7.1 because it didn't make the phone unusable, but I just flashed to 7.1 and it is still happening.