[Al Skierkiewicz]

John,
According to the manual, he Yellow LED indicates that the internal processor has determined that the position you have sent is out of range for the mode selected. The controller indicates it is capable of sending two different protocols to the servo outputs so this might be part of the problem. Remember that when a motor is asked to move, it produces a high current demand on the power supply, even for a short period of time. This might be related or it might not, but it is possible to draw the power down below 5 volts for long enough to upset the controller. The fact that you can move a servo once powered might be that it is just disabled, i.e. not recognizing the data it is receiving.