Bug#569662: Works-for-me solution

[Michael G. Hansen]

I found this thread:
http://bbs.archlinux.org/viewtopic.php?id=86627

Setting "network.protocol-handler.warn-external.http(s) = true" and then 
manually selecting /usr/bin/firefox as the application solved the 
problem for me. Trying to open links with the "firefox (default)" entry 
that was already present did not work for some reason.

Michael