EDIT: OK, looked a bit further and found the problem. Apparently you can only play with this content online! Ridiculous, wouldn't have wasted my money on it if I'd known that.

OK guys, I have had a slight problem with the 360 and downloadable content. I've looked up the error through Google and found a few cases, but none of them seem to really match mine. Here's my story.

I finished Crackdown a few months ago and about a month later hooked the 360 up to Live and downloaded the three things available (Four new heads, "Get Busy Pack" (that one with all the cheats "Keys to the City" or w/e) and that one with the new weapons and vehicles). Live said they all came in just fine, but when I booted up Crackdown it says YOUR CONTENT IS INVALID OR CORRUPT. Turns out the four new heads are fine, but the Get Busy and the other one don't work. Jump to today when I redownloaded both of the supposedly corrupt ones, go and boot up Crackdown again, and lo and behold it comes up with the same error.

I currently have a set-up that means I have to move the 360 from its usual position to access Live, so after downloading the content, I unplugged everything and set it back in its usual spot (without Live) then booted up Crackdown; do I need to have it connected to Live and boot up Crackdown, THEN it will work?

Yeah, I'm hoping you guys will be able to help me out on this. Thanks!

EDIT: Oh a bit more info. I use two accounts primarily on my 360: Chris, which is a non-Live enabled account, and is the account I play everything on. Then there's Christophomicus, the one I signed up to have a Live Silver account, which I only log into when I want to download stuff. So I move the 360, log into Christophomicus, download my stuff, unplug it and move it back, log into Chris and usually stuff works fine. Figured I'd just add that in case the question arises!