From a basic electronics troubleshooting standpoint. If something was working and now does not, and you are absolutely sure nothing else changed...
Look for a poor connection, the term re-seat comes to mind. Make sure everything with connectors is making a good connection. Jiggle or unplug, replug.
Make sure the batteries are all up. Lots of people freak out, it doesn't work and come to find the 9vdc battery was strong enough to light LED's, but not strong enough to power up the electronics.
Work on electronics first, servos second. No use trying to check servo power if the electronics are not acting right.
Try the PS2 on a PS2 console if available to test it.
That's all I got for now.
Jim Frye, the Robot Guyhttp://www.lynxmotion.com
I've always tried to do my best...