I tried uploading again without the motor shield/Bluetooth shield combo plugged in and I get that same, long error message posted above. Would it be a bad UNO board? What typically causes complications when uploading a sketch to a board?
The code compiles without errors.
I tried with a different USB cable and I just got this message
Sketch uses 6842 bytes (21%) of program storage space. Maximum is 32256 bytes.
Global variables use 346 bytes (16%) of dynamic memory, leaving 1702 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't open device "\\.\COM4": The system cannot find the file specified.