That it happened slowly in your case is relatively mysterious...
The poly fuse is designed to heat up and create an open circuit. Even in cases of dead shorts, it is possible for some current to continue to flow while the poly fuse heats up. It isn't a perfect system for catching shorts and doesn't "trip" to an open state. It does take some time for the internal elements to warm up and expand.
now im thinking of popping in a good old 7805 to see if that would fix it... might it work?
i just need to know the pin out of the regulator on the board..
If you have a regulated supply, just apply power to the 5V pin on the Arduino board. As for the pin-out of the on-board regulator, the schematics for all Arduino boards are available on the Hardware page.