Lpc2000

I've now got it down to any write to the EXTMODE register causes the 
processor to fail.

Even writing the reset value of 0x0 to it causes a problem. Below is 
the IAR assembler used to write the register with 0x0. I can't see 
anything wrong with this. However as soon as the register is written, 
see you later from the processor.

//  273 	EXTMODE = 0x0;		
   LDR         R3,??LPC210xInitExtIntPin_0+8  ;; 0xe01fc148
   MOV         R1,#+0x0
   STR         R1,[R3, #+0]


Has anybody else out there accessed the EXTMODE register on an 
lpc2129??