Lpc2000

Hi, I'm having a problem erasing the flash with IAP calls on my
lpc2146.  I'm making calls to the IAP, and get the chip id fine from
the IAP.  Next I make a call to Prepare the flash for writing (50d),
and I get CMD_SUCCESS (0d) as the response.  Then I make a call to
Erase to wipe some sectors where I know I have data (min sector=5  max
sector=14), and again i get CMD_SUCCESS (0d), but the IAP hasnt erased
anything, and has only spent 300us completing both those calls.

I'm running in User mode, I have interrupts enabled, and all the
handlers for the interrupts are in RAM.  Is there something I am
missing? Is there anything else I can try?

Any help is always greatly appriciated.

Cheers,
Mark