Tony,

I did not see where you indicated which pin on the PIC you are using for input.
As you probably already know that which pin you use matters in the answer to your question about what voltage will be recognized as a 1 (high) or 0 (low) by the PIC.

The PIC you are using has 3 types of digital input pins, each with different thresholds for low and high. Standard Inputs, TTL Buffered inputs and Schmitt Trigger inputs.

Table 15.4 of the DS has the Min/Max for Input Low and Input High for each of the pin types.

You probably already knew this, but just in case.

Regards,