B&W 802D midrange problem

Hi--I'm new to this end of the audio food chain and need a little help.  A friend gave me some really great gear--including a pair of B&W 802D speakers. The midrange isn't working on one of them and I think the problem is in the crossover.  I took the mid out of each tower and switched them and confirmed that the speaker itself is fine.  The connections both at the speaker and at the crossover look fine as well.
These have biwire connections and the same two terminals drive the tweeter and the midrange--and the tweeter is working, so I know those connections are good too.
Any suggestion about what I should do next?
Thanks.
Will