somehow my volume was very low for anything besides tv after an update on fedora 11.
took me a while to find it but after fiddling around a bit in paman - pulseaudio manager (sound&video menu) i fixed it.
check devices/sinks/properties/volume

firefox error

Error: Platform version '1.9.1.3' is not compatible with
minVersion >= 1.9.1.2
maxVersion <= 1.9.1.2

that's what you get on the terminal for updating xulrunner but not firefox (fedora).
would have been nice to get a proper alert window for that error or even better if dependency tracking had catched it.