Lpc2000

I have a strange problem with my ISR jump failing after I STOP/GO the 
CPU through the debugger.  I have a single ISR running off Timer-0 
that trips 10X per second.  When I start the code from 0x0 it runs as 
intended forever calling the ISR as it should. But when I use STOP, 
and then GO, the ISR never gets called again.  

I would have expected that it should jump into the ISR as soon as the 
GO is given since the Timer-0 Int flag would have already gone off.  
I don't understand why the ISR stops working after a STOP/GO.   It 
just quits branching into the ISR. The flags all say it should.  
Timer-0 is still running correctly.
 
Does breaking in with the debugger shut down ISR's somehow?
What am I missing?
 
Chris.