I've been involved with designing products that use PICs for around five years... in that time I've seen close to half-a-million products shipped. The products that have come back with a dud PIC I can count on the fingers of ONE HAND, and each one was attributable to a cause (invariably the installer). So the actual number of returns attributable to Microchip is ZERO.

We have seen duds that failed to program... but that doesn't count. However, in each case, those PICs were purchased from a 2nd-tier distrubutor or third-party reseller and we can't vouch that they hadn't played with them before we got them. We've had ZERO DOA's on PICs bought directly from Microchip.

I would suspect your client had been playing with the PCB or sticking his sticky staticky fingers where he shouldn't. This always assumes you've got a solid bullet-proof design and your programmer is half-decent and doesn't abuse the PIC to start with.

For your own piece of mind, check which pin(s) are shorted, check your software and TRIS settings that drive those pins (ie if it's an INPUT pin, ensure you're not accidentally setting it to OUTPUT) and look through the schematic connections to that pin to ensure you've not designed something silly that could cause an overcurrent, overvoltage or external short. If the pin is driving an inductive load, ensure you have protection clamping any possible back-emf's. Once you've satisfied yourself that guilt can't be laid at your doorstep, suspect the client did it... call CSI in your town and let them solve it (they usually solve any mystery however improbable within an hour - including commercial breaks)!