[Al Skierkiewicz]

Bill,
General failures have more to do with batteries then with anything else. Make sure that all the battery compartments are clean, i.e. no leaked batteries, all contact points are clean, and no foreign matter anywhere (like cookie crumbs). Then check that all the contacts press against the batteries tightly. You should not be able to turn the RCX over and have any batteries fall out. You might have to use a small screwdriver to pry some life back into the contacts. When in doubt make sure that the firmware is properly loaded or load it again. One of the students might have dropped the RCX pushing one of the batteries out of alignment for long enough to corrupt the firmware. IR illuminators in use on security cameras can play havoc with downloads so watch for cameras in your class room. If you have checked all of the above and you still have a problem, look for dings in the case (rounded corners, cracked LCD, etc.) indicating a drop. There may be no coming back from a cracked circuit board. As you know, the motors don't survive a drop either. If you can't easily back crive a motor, it is likely to have been dropped which either bends the shaft or deforms the motor case.