Comment 1 for bug 313393

I just fixed this upstream: http://git.0x539.de/?p=net6.git;a=commit;h=04ede417257b3201b68b683d13a69e07f8401eb8

Until this hits Ubuntu, you can probably set /proc/sys/net/ipv6/bindv6only to 0 to get IPv4 connectivity. (This seems to be the default on my machine, by the way, which is why I didn't notice this bug myself).