Can anyone see a problem with this?
Code wise, no. It should work as expected.

If you have a read-modify-write problem with a 100mS delay between toggling an output,
then you have a hardware issue with a boat-load of external capacitance on this pin.

Remove the DEFINE OSCCAL_1K 1. If it works, then your device programmer has most likely
erased the last program memory location of this PIC that had the RETLW xx, where xx was
the factory OSCCAL calibration value being returned in the W register.

DEFINE OSCCAL_1K 1 causes PBP to issue a CALL to location 0x3FF. Once at location 0x3FF
it should RETURN with the factory OSCCAL value in W, which gets loaded into the OSCCAL
register.

If this has been erased, the CALL causes a nasty loop from 0x3FF right back to 0x00, since
the RETLW instruction + the xx it should return has been erased.

This causes your program to loop continuously from 0x3FF back to 0, making it appear that
nothing is working.