The robots radios run at 900 mhz. Any cordless phone or other device that uses that range (which is very common) will cause interference.
The IFI system uses the team number to keep the robot from going crazy if there is interference. If the team numbers on the operator interface and the robot controller do not match, the robot won't move.
If there is intermittent interference, the robot will work most of the time and then appear to shutdown for a little while.
If you plan on doing more of these demos, you should make a "Yellow Dongle". This allows you to access more radio channels and increases the chance that the robot will work. There are instructions in the Control System manual. Dr. Joe also wrote a white paper about it:
http://www.chiefdelphi.com/papers/Ye...ngle011301.doc