It's indeed probably due to something special in 12.04 because on a relatively similar configuration with 11.10 and firefox 11 (firefox sync'd), this bug is not present.
So I've tried disabling the icons with "GLOBAL_MENU_NO_ICONS=1 firefox" but it didn't change anything. That said, I'm a bit doubting whether it really worked because the icons were still present in the menu. As for the backtrace, see the attached file (i've taken two bt at different times). It seems like all the time is spent in dbusmenu_menuitem_get_id() ... Is this hinting you on something? Now I'm going to try the included XPI with firefox-beta, and report later... ** Attachment added: "backtrace when firefox freezes" https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/964584/+attachment/2943554/+files/firefox-slow-menu.gdb -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/964584 Title: Firefox hangs temporarily everytimes it receives the focus To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/964584/+subscriptions -- ubuntu-bugs mailing list email@example.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs