Help- Co op in reach

Im trying to play reach with my friends, we got it at the midnight release.

Just 2 weeks ago I purchased the new Xbox 360 slim with the 4gb hard drive.

I currently have 3.6gb on that hard drive and a 250gb external i can pick from.

Whenever I host or try to join the party for co op it says “One or more players hard drive is not compatable or able to play this game type”

I do not understand what is going on? Any1 have a fix?

same problem, r we screwed? damn microsoft!!

i phoned -Yoink!- up and they said that i needed a 16gb memory stick to play coop but you said that uve got a 250gb external hd wtf?

Yeah, I have a 16GB memory stick and I get the same problem. Hope bungie can fix this soon.

this has really annoyed me, i have an external drive and 4gb MU.
still cant play co-op and firefight.