Xbox Live: Matchmaking disconnecting

Got a problem with matchmaking by the looks of it. I can sign in to my Xbox Live profile fine, even join a session of GTA Online (albeit on my own) and sit on the Dashboard without any problems. But when I search for a game with other players I get disconnected
from Live almost instantly.

I've also tried playing Gears 3 and the exact same thing happens: ridiculous lag for about 20 seconds before getting disconnected from Live again. I understand Microsoft have been having problems with Live the past few days but I can't find anyone else having
these issues. And the games I am playing are not EA titles (as the service update states that EA games are having problems at the moment).

Any help much appreciated, thanks!

EDIT: I suppose I should also say my internet is working fine; no other devices are having connection issues and testing my Xbox's connection brings back only positive results. Have tried clearing the system cache too to no avail, but have not gone as far
as re-downloading my profile yet.

:)

 

Matchmaking service alert

When I try to stream films on LoveFilm it keeps buffering before saying "sorry there's a problem" but not actually disconnecting from xbox live. When I ran a diagnostic I get the message "Matchmaking service alert". Any ideas what is going on?

 

Matchmaking service alert, three days so far...

I am apparently having Matchmaking issues as well, according to the Network Test. Trying to play Minecraft with a friend, but it keeps kicking them off of the server, and disconnecting our Xbox Live party. Tried resetting router, using wired connection instead
of wifi, restarting, etc. Haven't found a solution.