While trying to connect to MSN through a proxy server (proxy autodetected using libproxy), conenction can't be established.

The logfile (debugging, including libproxy debugging to be sure this is picked up right):

INFO:Butterfly.Connection:Disconnecting
DEBUG:papyon.transport:>>> OUT 15
Using config: 22gnome_config_extension
Using ignore: localhost,127.0.0.0/8
Config is: pac+http://gloapp04.tmf-group.com/proxy.pac
PAC received!
Using pacrunner: 25mozjs_pacrunner_extension
Pacrunner returned: PROXY 10.3.0.4:2323;PROXY 10.3.0.2:2323
INFO:Butterfly.Connection:Using proxy: http://10.3.0.4:2323
DEBUG:Butterfly.MailNotification:Initialized
INFO:Butterfly.Connection:Connection to the account dominique@leuenberger.net created
INFO:Butterfly.Presence:Setting Presence to 'NLN'
INFO:Butterfly.Presence:Setting Personal message to ''
INFO:Butterfly.Connection:Connecting
DEBUG:papyon.transport:<-> Connecting to messenger.hotmail.com:1863
INFO:Butterfly.Connection:Failed to connect, trying HTTP (possibly again with another proxy)
DEBUG:papyon.transport:<-> Connecting to gateway.messenger.hotmail.com:80
DEBUG:papyon.transport:>>> VER 0 MSNP15
DEBUG:papyon.transport:<<< VER 0 MSNP15
DEBUG:papyon.transport:>>> CVR 1 0x0409 winnt 5.1 i386 MSNMSGR 8.1.0178 msmsgs dominique@leuenberger.net
DEBUG:papyon.transport:<<< CVR 1 14.0.8089 14.0.8089 14.0.8089 http://msgruser.dlservice.microsoft.com/download/7/5/8/758BFCC9-1744-48F7-8162-E0AC1E7BF5C8/en/wlsetup-cvr.exe http://download.live.com/?sku=messenger
DEBUG:papyon.transport:>>> USR 2 SSO I dominique@leuenberger.net
DEBUG:papyon.transport:<<< GCF 0 5131 5131
	[payload]
WARNING:papyon.protocol:Notification unhandled command : GCF 0 5131 5131
	[payload]
DEBUG:papyon.transport:<<< USR 2 SSO S MBI_KEY_OLD BzFbVr5Xcwsh8ZlXjJIwgz3jVzB1CzZj7CQ8DafAvDP+jt+bqbey5QrjeM4ueaK8
WARNING:papyon.service:Transport Error :1


At this state, empathy remains in state 'connecting' with the green ball flashing, but no further output happens until I disable the account, when a proper disconnect happens:
INFO:Butterfly.Connection:Disconnecting
DEBUG:papyon.transport:>>> OUT 136

empathy-2.30.1-87.2.x86_64
telepathy-butterfly-0.5.9-20.2.noarch
papyon-0.4.6-16.2.noarch