>Also if I wait a day, burning works fine again,
>for about twenty or so burns.

This strikes me as a problem with LV programming bit being set, and the PGM 
pin not being held in the correct state.

What programmer are you using? I seem to remember someone recently having a 
problem where they found their programmer was illegally changing some bits 
in the config word from what was specified, and doing something like this. 

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