Initialize P2?

[Gundorf Dunderklumpen]

I have been shooting a feature with the HPX and 4 16gig cards. I am using FCP2 with mac book pro and the Duel Systems adapter. I am getting an "Initialize P2 card? error when I load one of the cards to the computer. I tried to format it in the camera but I cannot select the slot that its in to format (its not highlighted) The card has worked fine before and the otheres work fine...???/

any suggestions?