Comment 28 for bug 226470

Bug 370915 is another excellent description of the same problem.

I have some observations to add: In my experience, it is not strictly required
to run out of memory and start chewing up swap space before the problem occurs.
For example, at the moment of this writing I have 3G ram, 1.4G used, 0G swap
used and I already have two disembodied Untitled windows popping up.

I can also confirm the console error messages syndrome, although I had not made
the connection with the disembodied window problem before.

I can however confirm that the cobination of X and my 2-3 firefox processes are chewing up quite a lot of cpu while this is going on.