FIXED!

Thank you both of you for your responses. My contact also suggested checking the status of the oscillator crystal with an oscilloscope and the configuration settings. The settings appeared correct to him, so I went ahead and uninstalled and reinstalled the programmer software (updated from 4.50 to 4.51). The update must have reset all the configuration settings because it worked! Both boards are now up and running again with the original software that they crashed with.

The problem appears to be that, in the case of a crash of the melabs programmer software while it is programming, the configuration settings get jumbled or lost and will program each subsequent board with the wrong settings even if you restart the program or try another set of code. It is technically beta so I don't blame the programmer. Hopefully crashes can be better handled in the final version!