I hate to be the bearer of bad news but I have a couple of freinds who got the dreaded 3 red lights and it usually means imminent xbox death.I think you will be sending it in for service in the near future.
My sp campaign it totally unplayable.I cant even get past the training mission.If I skip the training mission it freezes right when I hop off the chopper.I have been all over the ubi forums and They are basically ignoring the issue.Their so called tech support is just an automated finger pointer...