Hey guys! Thanks for the quick responses!
Nothing on the board seems hot to the touch when the bot dies.
As far as I can tell, voltage seems consistent. I'm not seeing a drop anywhere. Here's how I'm testing:
(bear in mind I'm just some dope with a voltmeter and not an EE or anything)
1. I'm attaching my red alligator clip on my meter to 5V and the black one to ground. Reading stays constant around 5V, even after the robot stops moving.
2. I'm holding one clip to the metal tab on the inside of the 9V barrel plug, and keeping the other attached to ground. Reading is constant around 6V, whether the bot has stopped or not.
Sooooo.... according to this: http://www.arduino.cc/en/Main/ArduinoBoardDuemilanove
The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.
...my bot is running right on the edge of reliable board behavior voltage. Does that seem correct to you guys?