I have now tried 3 Arduino Duemilanove boards on 3 different computers, 4 different USB cables (3 known good, one brand new), and 2 different versions of the software (022 and 1.0.3). WTF?? everything was working fine last week, now NOTHING works. Same errors each time, with each board. Help...please...
Ok, you need to proceed in steps. First is to see if your USB drivers for the arduino boards is OK. So perform the "loop back test".
install a jumper wire from ground to reset on the board
install a jumper wire a from pin 0 to pin 1
Plug the board into the PC
does the PC acknowledge the USB connections?
If so open the arduino IDE, select the proper com port, open the serial monitor, then anything you type into the send window and press send should be echoed back in the receive window.
If that works check out each board using the same jumpers and rechecking for the proper com port number selection, and checking for proper loop back characters.
Report back your findings.