Looking forward to a night of gaming with your mates? You might be disappointed, it looks like Xbox Live has had one pint too many and is spoiling the party for everyone.
According to the Xbox Status Page MS are working on a fix:
Are you running into issues creating or joining multiplayer matches? Additionally, are you having trouble joining parties or sending party invites? We’re aware of the issue and hard at work to find a fix. Thanks for being patient, Xbox members! We’ll provide an update as soon as we have more information.
Hopefully we won’t have to wait too long for a fix…