Jack,Still can't get it to work. So I am buying the Keyspan. I'll let you know if it works.
Managed to update my Netduino Mini today using a Synapse Netduino Mini Breakout board that I got from Jameco.
I had a few problems, but finally got it to work.
The board connects via USB, but must be selected to RS232.
It showed up as Com3, ended up using Sam-Ba 2.11 due to communication error that I got with 2.12 (may have had the board selected to TTL at the time, not sure). I could have tried a higher voltage supply to the breakout but it did update at 5 vdc from the USB.
Tested the board okay after I figured out that Pin 17 was PWM0.
Good luck,
Chuck