convert sometimes hangs on multi-core

Hi there,

while I was trying to perform some batch conversion of images I experienced
several hangs of the command-line tool "convert" where both CPUs of my dual-core
machine would go up to a 100% usage and nothing would happen. However,
explicitly disabling one CPU helped circumvent the problem. With only one CPU,
the batch conversion runs fine.

I've used convert like this:

convert "$INPUTFILE" -separate -swap 0,2 -combine "$OUTPUTFILE"

Whether convert hangs or not does not depend on a particular file. BTW, I'm on
Mac OS X 10.6.3, using a Dual Core MacBook Pro.

Regards,
Alexander