Add this line before your main loop:

RBIF var INTCON.0

Add these two lines to your flash subroutine:

@ MOVE?BA PORTB 'Read PORTB by placing it WREG
RBIF = 0 'Clear the interrupt flag

Also, read the pic datasheet on interrupts and under the I/O Ports section. You should find were it mentions both of items added to the ISR.

Steve