Hi Stephen,

This Instructable has a pretty good list of things that might cause that error:

http://www.instructables.com/id/A-solution-to-avrdude-stk500getsync-not-in-syn/

When using the Windows version of the Arduino IDE, I've also seen the COM port assigned to the Arduino jump back
and forth from COM3 to COM4 when I reconnect it, for no clear reason. So double-checking the assigned port in the IDE is good.

Best of luck,
John