I bought my 360 on roughly the 4th of february, two weeks ago today I believe or something, it was second hand, and I deleted the two exsisting profiles and made my own, signed up to th free mon of Xbl Gold. Then I hear from my brother over MSN this morning (I'm at my friends house) that when he tries to play Halo 3 onlne it says "You must have xbl blah bkah blah" But I haven't had it for a month, and KI have two friends who got free months from new profiles in February and I was playing on one of theirs on CoD 4 early thsi morning. Edit: And am now, and this profile was made awhile before I got my 360.
I even got an e-mail about 20 minutes ago from Microsoft telling me that my Gold subscription is ending o the 4th March, but it doesn't seem to be working still.
Why is this?

" You Must have xbl Blahblah blah"
That Bit really helps alot...

Well that's all my brother told me literally

"when I tried to connect to halo it was like to play online you must have xbox live"
Edit: Well i just wsaw my bro signin on my friends Xbox, so it may be wrking and justhave been temporarily down =( I'll ahve to heck if he is actually on Live

Maybe if it was second hand it could be a dodgey 360 or the previous owner may have used part of the free trial (was it the free trial?)...or if it dont work just upgrade to a higher subscription like me 12 month gold membership...hope this helps?!?!

This is why I only buy new electronics.

Are you sure you got the free month? Standard an xbox 360 lets you sign up 4 accounts which can all use the one month free, maybe the person who had it before had more than 4 accounts?