Trouble with MP Ranked matches

I have Prey on the X360 [I have noticed everyone here seems to have it on PC] but can't seem to get into Ranked matches hosted by other people, everytime I get the same error message about 'not having the right content' or somesuch. I've tried downloading everything in the 360-Prey-Marketplace, but nuthin' works. [when I host, others can join, but my friend has the same problem, even though we've both downloaded the patch you get presented with when you start the game up]


Anyone got any ideas?