Mac - port problems

I have three boards, an iDuino, a stickDuino, and Decimilla. When I download, the stickDuino finds the correct port but not iDuino or Decimilla. I have corrected this problem before but can't repeat the process.

I should have added that this problem occurs with both my MacBook and MacMini. After months of problem free use, my Arduino Deicimilla is driving me bananas. I have downloaded older versions and drivers, hoping to find a solution but in vain, same problem again and again.

I have tried the boards on a PC with the same results: StickDuino uploads, the Deicamilla and iDuino won't. This is a complete mystery!

What happens?