I keep getting kicked off multiplayer!!!

Okay here the problema. Every time I want to play a player match on multiplayer it kicks me off for the most random reasons!
-It sometimes says call of duty sever isn't availible
-It sometimes says i must be singed int xbox live, when i already am!
-It also says i must have an active xbox live conection when i do have an active connection!
If this keeps up I may never be able to play black ops again! :shock:

Please help!