This week I joined some friends playing Borderlands again. Of course playing co-op the game suddenly is a lot of fun again.

Motivated by this I wanted to continue on by myself, but found that my DLC is behaving strangely: I originally downloaded it (all four) from a friend's account, as we share "the load" for DLC we both like. When I joined an online game (robolution, moxxi) everything worked fine, but when I tried to enter the dlc areas in single player it told me sth like "dlc not installed".

Has anybody an explanation for this?