Neero is right, the removing of the battery forces the N8x0 to do a hard reset or something, not just a soft reboot. Im guessing that something or another was corrupted, and killing the processes helped. If the N810 ever gets laggy/slow, I find it very helpful to just yank the battery, wait 20 seconds, and pop it back. I think this clears the memory and stuff, which probably got clogged down with leaks from apps.

Also, you can try to reboot as root from xterm. This seems to work much better than the "Switch Off Now!" option in most cases.