Obviously, you move your gamertag from your 360 to your friends 360 often. This is one thing you should NEVER use the "Recover Gamertag" feature for. This can corrupt your gamertag.
What you should do instead is move your gamertag onto a USB stick, and take that to your friends house. This has various advantages over recovering your gamertag:
It's much quicker. Instead of waiting for the gamertag recovery, you just plug the USB into the 360, and you can play straight away.
It's more reliable. It's much less likely to be corrupted due to network problems, or other issues.
It's more secure. I'm sure your friend is trustworthy, but unless you delete your gamertag from your friends Xbox before you leave his house, he has full access to your account until you recover it again on your Xbox. During
that time he can do whatever he likes to it, including something that can get YOU (not him) banned from Xbox Live.
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