Egads! You must be using lead free solder to get results like that. Funny thing about tin is it grows whiskers. Do you have a 3 terminal resonator ? At this point I would probably bend the 2 legs of the PIC associated to the OSC. and attach them to a resonator with a point to point ground wire, or use an external OSC. Check the 2 pins of the board with PIC removed for capacitance, I would bet it is loading down the PIC's OSC until it does not work. Why would it run once ? Maybe in initializing it gets more power than after it starts. I am thinking there is such low impedance on the OSC circuit that it does not run.