Seems the hang is related to Trinity's kgtk module. My apologies for the inconvenience.
Others who drop by here, the fix is: sudo apt-get remove kgtk-qt3-trinity ** Changed in: firefox (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1010208 Title: Firefox 13.0 on Lucid hangs very often, sometimes a JavaScript hang dialog is displayed To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1010208/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs