Firefox and Mozilla stopped working

[Benjamin Walkenhorst]

Hello everybody,

I am using FreeBSD 5.3-RC2
I recently grabbed a recent ports-tree via ftp and happily installed 
firefox-1.0rc1.
After the build process said "Building Chrome Registry", firefox-bin was 
eating all free
CPU-cycles.
When I rebuilt, the same thing happened.
Even more weird, Mozilla won't run anymore, either.
Now I get the following error when I want to start firefox or mozilla:
##############################################
=== 09:59:45 krylon at neuromancer:~:: firefox
[: Abort: unexpected operator
Fatal error 'Spinlock called when not threaded.' at line 83 in file 
/usr/src/lib/libpthread/thread/thr_spinlock.c (errno = 0)
Abort trap (core dumped)
##############################################

What have I done wrong? I already uninstalled firefox and mozilla and 
reinstalled the old ports tree and rebuild
firefox 0.9.3. It still gave me that error.
I reinstalled mozilla, it also gave me that error.

What is wrong here?
I have already done an upgrade to 5.3-RELEASE, but the problem persists.
(In case it matters, I have an SMP machine as well as an SMP-enabled 
kernel.)

Has anyone had similar problems? Or am I just too stupid?

Kind regards,
Benjamin