I have a "strange" problem with a 16F870.

I have a piece of code that gives me an error in the programmer application. But this error only happens if I introduce the line "ON INTERRUPT GOTO ISR". I remove that line and the PIC gets programmed correctly.

Code:
...

INTCON = %00100000 ' Enable TMR0 interrupts
OPTION_REG = %00000111 ' Initialise the prescale
TMR0 = 217 ' Load TMR0 register
ON INTERRUPT GOTO ISR
INTCON = %10100000 ' Enable Interrupts

...

DISABLE
ISR:
  TMR0 = 216
  
  ...	
  
  INTCON.2 = 0 ' Re-enable TMR0 interrupts
RESUME ' Return to main program
ENABLE

END
Any ideas?