I had a similar thing the other day. I was playing one day, then the next day, nothing. Apparently I didn't have gold membership anymore despite my dad paying for a year of it back in December/January. We fiddled about with settings but still nothing. To be honest I can't be bothered with it, I've stopped using Xbox really, it's just sat there not doing much. Games consoles aren't designed for people to enjoy, they are just there to snatch money from people without them noticing.