I am using a mid-2012 MBP 13in with no retina display, running OS X 10.8.3. Everything was fine until I was watching a video clip on Facebook. Everything just froze, except the mouse pointer can still move, but I can't do anything else. So I was forced to long press the power button to shut the machine down. After that, the whole system was ridiculously slow.
I can boot into my own account, but starting/running/closing any program takes ages. Also, when I tried to mount a .dmg. I was given a error message like "No suitable file system." I know I can just re-install the by booting into the recovery partition, but I'll take that as my last resort.
Here are more screenshots of the Activity Monitor:
Best Answer
It turns out to be a hardware problem. After getting frustrated with the extremely slow response, I reinstalled OS X via the recovery tool. But that doesn't last long - it starts to get slower (but not as slow as this case), and the Disk Utility complains that "This drive has a hardware problem that can't be repaired." So I send my MacBook back to Apple and they replace the hard-drive for me and it was covered by warranty.