FEZ Cobra crashing & not reset by watchdog timer

I run my FEZ Cobra with 7" display & watchdog timer set to 5 sec.

One of my customers reports the display freezes in some situations.
FEZ Cobra however is not reset by the watchdog timer?

Is it possible FEZ completely locks up and even the watchdog timer is not triggered in such case?

Any of you guys seen this before?

TIA

Jos

Are you sure it is not power related?

Also, watchdog depends on how you are using it

I have a timer displaying date & time in a text field.
The text field is invalidated to make the text field displayed
This timer also resets the watchdog

Is it possible the timer keeps running but the display is no longer refreshed properly?
How could this happen?

Maybe an exception caused the program to end but timer kept running?!