And just to make sure that all the bases are covered:

Are you sure that the proper COM port is free when you try to connect? Is it still tied to your other empeg? Is another program grabbing the serial port? Hyperterminal won't see anything if another program has control of the COM port. Programs that can hog your COM port can include emplode, jemplode, the logoeditor or any program that works with your cell phone or Palm pilot.

Are you using the same power supply for the "good" empeg and the one giving your problems?

Like Tony said, I would try to apply a HiJack to the thing, it can't hurt.