I am struggling (rather gasping :-) at a problem where OS seems to hang completely.

So far, I have seen two different behaviors:

One where Interrupt flag was disabled and HLT was executed. See, Jan-19-2012.bmp.

Another where Interrupt flag was enabled and HLT was executed. See, tb1-hang-no-access.bmp

In both cases, system did not respond to ssh/keyboard/mouse. We are using procnto-smp-instr. I don't have access to 
source code. We are running 6.4.0.

tb1-hang-no-access seems like a situation where IDLE task was running.
Jan-19-2012 seems like a Blue Screen of Death / Out of Interrupt event.

Any one can confirm and give suggestions on how to debug this further?

I have a JTAG connected to the system that shows Jan-20-2012.bmp

Please help. It seems like a case of spurious interrupt. I want to know how can I determine which interrupt is causing 
this. 

Thanks a bunch.