this appears to have been corrected in subsequent xulrunner releases, i.e., i have 1.9.1.5 in f11 and it's fine. if it re-appears, please file a new report and we'll track it down.
This cannot be done due to the nature of keyboard focus in GTK/GNOME. Alt-anything has prioritized reactivity and the menubar wins. If anything, I'll take out the underlining which is having no effect. Be aware that simply hitting makes the search execute.
