Melanie's Olympic code uses ON INTERRUPT, so you cannot change the GIE bit manually.

Clearing GIE tells PBP that an interrupt has occured and it will be processed immediately. Even though no interrupts actually triggered.
GIE will then be SET again, looking like it was never cleared to begin with.

If you don't want a section of code to be interrupted, wrap it with DISABLE INTERRUPT/ENABLE INTERRUPT.