So much for my motor regeneration hypothesis...
It's still a good warning to teams, though - using a typical lab-type power supply (eg switching supply with lots of overcurrent/voltage protection) to drive a motion control system WILL help to kill nearly any motor drive that you use. You should either use a battery to power the system, use a shunt load or use a really simple linear supply or similar that can "absorb" any regeneration currents.
Here's an example of a shunt load. This is NOT a good example for a FIRST application (wrong voltages) -
http://www.animatics.com/catalog_pdf/48-49.pdf
Russ