I've never used that pin definition for overflow... did you try just looking up the register in the part schematic?
If you use this reference for where pins are on the part as compared to the pinout of the control board you can find that the second digital i/o pin is routed to RB3 on the microchip....
then if you look at the processor manual... that pin has a unique interrupt on it (unlike the second half of port b's external interrupts)... and its priority register byte is in INTCON2, so the bit to set the pirority is "INTCON2bits.INT3IP"
here's the line of code i suggest switching out for the one you had:
Code:
INTCON2bits.INT3IP = 0; //sets RB3's interrupt to be low priority
need anything else... hit me up with pm or email.
-q