[chirp_users] Using CHIRP with Kenwood TH-F6A

I am trying to use CHIRP to program my Kenwood TH-F6A and so far it is not working. I have the Kenwood USB cable from Valley Enterprises and I have gotten the FTDI driver software installed on my Windows XP machine.

I start CHIRP and select Radio -> Download from radio. I get a dialog box into which I put the Port, Vendor, and Model. I then click OK. The radio's transmit light flashes once, then the dialog box in CHIRP goes away and nothing happens after that. Any ideas?