For some reason, my interrupts have stopped working.

I think it's something to do with Program memory bank 1 - my code's
gotten to the stage where I've had to start dumping routines into the
second bank - calling them from the first bank.

When I call a routine in bank 1 and loop there waiting for an interrupt
driven timer to time out, it never does - it just goes round and round
the loop.  The SCI interrupt and the keyboard interrupt don't work
either.

What's happening?  I've checked and double checked that GIE is set and
doesn't get disabled anywhere else - and I presume that when an
interrupt happens when the code's in page 1 that it'll still jump back
to the interrupt vector at 04h.

I'm saving context ok in the interrupt (W,Status,FSR and PCLATH) - and
in fact the interrupt code never seems to get run at all (I put a port
flag in to check and it never gets set)

Any ideas?
--
Jim