Well, I don't really know.

But, the datasheet for the 18F4550 shows 12 different interrupts from the USB module that all funnel into the single USB_INT. So I doubt it's that easy.

But if I were going to try it, I might set the ...

TRNIE: Transaction Complete Interrupt Enable bit

and see what happens.

DT

Added: and then all the others just to be sure.