Not sure where I should be asking about this, but is anyone else
seeing:

firefox-bin: Error detected by libpthread: Invalid mutex.
Detected by file "[my-source-tree]/src/lib/libpthread/pthread_mutex.c", line 133, function "pthread_mutex_destroy".
See pthread(3) for information.

This has happened repeatedly with firefox-gtk2-0.10.1 on 2.0_RC4.
It did not happen with 0.9.3.  Using menus or links that open popups
(gallery....) tends to provoke it.

I'm running again as

PTHREAD_DIAGASSERT=AeL firefox-gtk2

hoping that ignoring what is perhaps a double-destroy is not fatal.