I was a long-time ubuntu user and switched to Mint since Celena, and now I'm running Daryna. I'm finding it jolly good also .
I have this problem I also had back with Celena: at times there is a temporary (like three seconds) freeze of the system (guessing it is X). I can move around the cursor, which remains in the shape of when it froze, but nothing happens. Then all of a sudden all the commands issued during the freeze are done all at once (like scrolling, clicking on close window, typing on the keyboard).
Other times I'm less lucky, and the system freezes completely: I still can move around the mouse, but absolutely no input is taken from anything. So I cannot restart the server via ctrl+alt+del, or switch to terminal via ctrl+alt+F1. Alt+print+(S,U,B) to synchronize and unplug the disks and reboot works, but nothing else. As it turns out, the system is not really frozen: sound playback goes on for example, and not only. I installed open-ssh and found out I can still ssh into my machine and restart the X server, restoring everything. This obviously depends on being on a network and having at disposal another machine. In any case, that's why I suppose the problem lies in the X server.
So, long story short: I think I'm quite a bit linux-savvy, but not completely so I'd like to know how can I diagnose the problem, more specifically: are there any logs I should go to and catch next time this stuff happens to me? I'd like to be more specific than just "my system hangs"...