Oops, I forgot to say I found this problem with Mozilla 0.9.3 release.
confirmed 2001082908 linux CPU utilization is very high even after closing JS console. closing all windows doesn't leave any rogue mozilla-bins, though.
*** This bug has been marked as a duplicate of 85831 ***
mass verification of duplicate bugs: to find all bugspam pertaining to this, set your search string to "DuplicateBugsBelongInZahadum". if you think this particular bug is *not* a duplicate, please provide a compelling reason, as well as check a recent *trunk* build (on the appropriate platform[s]), before reopening.