If you flip the Arduino duemilanove "upside down"
you see 4 points where the USB is soldered into, does anyone know which point is which?
USB to PC
^^^^
| ----------
| (1) (2)
| Wallwart adapter plug->
| (3) (4)
| ----------
I'd hate to have to destroy a USB plug to map the points...
thnx
I'm having trouble understanding your sketch of where the parts are on the board so I'll come up with my own numbering 
Looking from the top of the board
+------------------------
|
+-+
| 3 2 U 1: +5V
| 4 1 S 2: D-
+-+ B 3: D+
| 4: GND
|
|
|
++
| Power jack
++
|
+---------------------
yours is a much better ascii sketch
thanks at ton!
you could try taking a multimeter to it and measure resistance, when you get a reading that is valid, then you know what is paired to what (not sure if that will work, but it seems like it should)
wait, didn't see his sketch. nevermind
Schematics and PCB layout available here: