PIC programs, resonator resonates, but does not run code.

[Dave]

Let's look at the code that works. Maybe theres something you left out...

[Darrel Taylor]

The 20-pin version has separate AVSS and AVDD pins.
Did you connect them to VSS and VDD?

[jmgelba]

Fixed!

So it would appear if you use the auto insert serial number feature it changes your config bits during programming. This applies to the U2 programmer software. Uncheck this feature, problem solved, and the design functions just fine.