Cyanogen nightly bug!
I've been having this issue for a while (I think I noticed it from the 20140416 nightly, not sure though). I experience random crashes here and there (everything will freeze and then the UI will "reset" itself), but they mainly happen when I try to pull down the notifications bar after unlocking my phone. It's pathetic that this happens, as I'm sure it's not a big deal to fix!!!
If this is in the wrong thread than please move to the correct section. As I'm a new user here, I can't post in the development section, unfortunately.