Firefox/Thunderbird and SSL not working with libthread_xu

[Jordan Gordeev]

Simon "corecode" Schubert reported XXX some months ago an issue with 
Firefox/Thunderbird and SSL when using libthread_xu as the threading 
library:
   http://leaf.dragonflybsd.org/mailarchive/bugs/2007-12/msg00144.html
I started looking into the issue and found something that seems like a 
bug to me.
I traced an execution of firefox with ktrace and observed something 
strange. Below is a commented extract from the 'kdump -T' output.
// thread #4 calls umtx_sleep on 0x2a92f664
// thread #4 never returns from this syscall, according to the kdump output
75875:4    firefox-bin 1207996217.713757 CALL  umtx_sleep(0x2a92f664,0,0)
// thread #1 attempts to wake up thread #4
75875:1    firefox-bin 1207996244.646643 CALL  
umtx_wakeup(0x2a92f664,0x7fffffff)
// I terminate the process
75875:5    firefox-bin 1207996413.782573 PSIG  SIGQUIT SIG_DFL

The expected behaviour is for thread #4 to wake up when thread #1 calls 
umtx_wakeup.

I'd appreciate any feedback on the issue.
If you need information about my environment, I'd be happy to provide it.