Hi,
I don't have a definitive answer for you but here's a couple of things.

First, if you haven't already, make SURE that you have Control of the pin where you have the LED connected. Make it blink a couple of times at startup or whatever.

In case there's something weird with the .BIT modifier I'd try the "standard" PIR4.0 syntax. I'm not sure it's even any difference under the hood but just to make sure.

In your main code, do:
Code:
IF PIR4.0 = 1 THEN
  TOGGLE LED
   PIR4.0 = 0
ENDIF
That'll tell you if the interrupt flag gets set or not.

/Henrik.