[avr-gcc-list] Reset on TIMER1 Overflow

[Kevin Neff]

I have an ATMega128 that is resetting unexpectantly after
about 10 seconds.  This is a surprise because

  1.  The WDT is off--fuses are correct & wdt_disable() is
      called early in the program.

  2.  The interrupt handler (TIMER1_OVF_vect) gets a
      value from flash and places it in TCNT1H and TCNT1L
      (in the correct order),

  3.  A debugging signal (a 0.5-second buzz, LED flash) in
      the interrupt handler does not get executed.

  4.  Disabling the overflow interrupt for TIMER1 (TIMSK,
      bit 2) fixes the problem.

  5.  My default interrupt handler overrides resets but also
      does not seem to be called (buzzer doesn't sound, LED
      doesn't turn on).

Maybe I'm missing something obvious.  Anyone have an idea
where I could start looking for clues?

--Kevin