"neally@darkstar:~$ tar xvfj firefox-3.6.13.tar.bz2
tar (child): firefox-3.6.13.tar.bz2: Cannot open: No such file or directory
tar (child): Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error is not recoverable: exiting now "
Either you're in the wrong directory, or you're typing the filename wrong.
in the terminal, and see if firefox-3.6.13.tar.bz2 is in the output