NG Rev C External Power Problem?

We have a group of boards from Sparkfun (e.g., 9158, 9778, 9898) and we're having trouble running programs with an external power supply. A simple program such as the default LED blink is running fine through USB power, but is not running after switching the jumper and using an external power supply (12V, 600mA). Is this a possible problem, is it a know problem?

Thanks, Casey

hi casey, you're not the only one with this problem. i tried the pulldown resistor suggested in this thread and everything worked:

Thank you, we'll try that.

Casey... next time email me directly.... :)