PIC ADC GOnDONE never clears
Thanks for the response.  Yes, it was the fact that I had ADC interrupts enabled with no ISR.  After disabling interrupts, setting and polling the GOnDONE bit now works.  As for GOnDONE versus GO, the PIC header file defines both for the same bit, and either one works.  Perhaps they do this to maintain compatibility with other versions or libraries.