iceweasel "freezing X"

[Attilio Cucchieri <attilio@ifsc.usp.br>]

Hi,

  I have installed Debian etch, basically using the packages
from "Standard" and "Desktop", on two different computers.
In both cases, if one starts sevaral Iceweasel windows, the
X session gets frozen when the windows are closed (only when
they are closed!). The two PC's have

PIV 2.4, 512 KB cache, 512 MB memory

PIV 2.8, 2 MB cache, 512 MB memory

Note: it is only the X session that gets frozen. When this happens,
I can still connect to the machines from another PC and work
on it.

Any ideas of what's going on?
Best
  Attilio