I've had a lot of problems with my Xbox over the past month, for starters the day after I purchased Gears Of War 2 the machine red ringed and had to go away for repair. This took about a week and my Xbox came back with one months free Xbox Live.
The last time I used Xbox Live was over 6 months ago but with a new game I decided it would be fun to play online again. When I tried to redeem the Xbox Live Code I was given an error message and had to call Xbox Support.
It turned out that because I cancelled my credit card half way through a year long Xbox Live subscription they had locked my account (tip: always buy the pre-paid cards rather than using your credit card online). It took them a further two weeks to unlock my account.