From ETN #22:
Symptom: PIC16C55A, PIC16C57C and PIC16F57 devices do not verify correctly
using the PICSTART Plus. When a blank device is read, program memory
values of 0xBFF are reported.
Problem: The OSC2 pin on the PIC16C55A, PIC16C57C and 16F57 tries to
overdrive RB6. This causes invalid voltage levels for verification.
Solution: To program the PIC16C55A, PIC16C57C and the 16F57 in DIP
packages on a PICSTART Plus, a modified adapter must be used. The
adapter can be created using a 28- or 40-pin ZIF, LIF or standard
socket by cutting the connector pin that corresponds to pin 26 the
device. After creating this modified adapter, secure the device in
the adapter, then place the modified adapter in the PICSTART Plus.
This adapter should only be used when programming these devices.