Whoops, that wasn't right AGAIN.

You'd think I'd have learned my lesson by now.  Once again I was fiddling around with power supply (this time I was trying to reduce noise from the USB or computer) and managed to kill my fancy-ass FTDI USB<->Serial chip.  The whole part was $15 (making it the most expensive component in the device, ouch!)  but I can get the chip itself for $4+shipping.   Looks like it's time for another sparkfun order, and then I get to learn how to solder SMDs...