I find your post confusing. You say you got a 5 wire DKU-5 but then show six lines. Does your cable have VCC, GND, RxD, TxD, DTR (auto-reset) all at the connector with no extra work? If so that's amazing. Usually you have to work a little to get VCC and a lot to get DTR.
@ everybody who has used DKU-5
I was lead to believe by Tim Small's article that the DKU-5 transceiver had to draw power from the phone at 3.3V. Are those you using the DKU-5 having to supply 3.3V to it? Having to supply 3.3V to the cable would complicate things when working with 5V Arduino.
I wrote an article on modifying a CA-42 to have VCC, GND, RxD, TxD, DTR (auto-reset). It was first on uChobby. Now it's on my blog and linked to by Hack A Day. Please leave a positive comment if you find this useful.