Blade nic shows disconnected?

I have an ESX host running on an M610 with Dual KR X-520 Mezzanine cards.  My IO modules C1 and C2 are M8024-K 10GB switches.

One of the nics on the card is up, and the other shows disconnected.  The disconnected nic is mapped to a port on module C2.  ESX is using the same driver for both ports.

From the C2 switch, the port shows enabled but down.

I've reseated the card and the server, no joy.  I have other servers with identical hardware/software configurations plugged into this chassis that aren't having an issue, and the down nic has worked in the past.

I'm thinking next steps are to replace the mezzanine card.  Reseating the switch makes me nervous.