This could be a number of things.
First thing I would do is upgrade / update your dashboard. You can do this by connecting to xbox live and attempting to make an account. Before you get too far, if need be, your dashboard will be updated.
The next thing I would do is make sure your not using an outdated mod. Grab
Krayzies Ndure 1.1 for your make and model from our download section :
http://www.smdepot.net/files.phpLet us know how it goes.