Lpc2000

We are developing on a Ashling EVBA7 with a LPC2106 using the IAR 
EWARM 4.11A. We are using nesting interrupts. We have some code 
which seems to run fine on 1 of the EVBA7 boards but branches to 
0x7FFFE254 on the other 2 as soon as interrupts are enabled. They 
are all using the 14.745MHz xtals and the code is setting up and 
using I2C, Timer0 and Timer1. We are setting the PLL to run at 
58.98MHz and the VPB is set to 1 to run the VPB at the same speed as 
the processor. The same problem occurs whether we run the code in 
flash or RAM.

I have tried everything a can think of to track down the cause but 
so far no luck.

This is NOT being caused by an exception. All of the exceptions 
except IRQ point back to itself in the startup code.

Does anyone know what may be causing this to happen.

Thanks
Rick