File Transfers: Listening on v6 only
Gajim 0.12 (Win32) under (at least) Windows Vista 64 binds only to IPv6 interfaces:
D:\>netstat -an | grep 28011
TCP [::]:28011 [::]:0 LISTENING
There are no listeners on the IPv4 interfaces, and therefore it's impossible for the peer to establish a connection over IPv4 at all.