Using an ATmega640. It worked fine.
Enabled WDT using latest version of AVR Studio b623 using Fuses tab.
My ATmega640 would then reset crazy fast. As expected.
Now I go back to Fuses and remove the check to WDT.
My ATmega640 still resets crazy fast. Despite AVR Studio claiming its off, it won't actually turn WDT off!
(power supply is fine)
Anyone seen this problem or know what I'm doing wrong?