[tblake]

Sounds like a bad spot on the starter. Two things you can try.

-When the car doesn't start in park, attempt to start it in neutral. If it starts, you have a failing neutral safety switch (PRNDL switch)

-when the car doesn't start, have a buddy hold the key in the "start" position and you measure the voltage at the starter "S" terminal. With a voltmeter or test light, put the ground lead on chassis groung, and the positive lead on the small terminal with the purple wire connected to it. If you get 12V when when the ignition is in "start", you have a bad starter.