Yes, the old Arduino was a Mega.  I finally got the setup working.  Apparently there was a newer version of the Motor Library, but I didn't notice that it was new, since there are no version numbers for the library.  I only noticed when there were more examples in the examples folder.  In any case, thank you for your help; I really appreciate it.

I am trying to use the Adafruit motor library with my Arduino Mega and the Adafruit motor shield.  From what I know, I think the library is only compatible with older versions of the Arduino software.  However, I have tried using version 1.0, and that didn't work.  I have already installed the newer drivers for the Arduino, and that seems to be the problem.  Is there a way that I can reset the drivers so that I can install an older one from the 1.0 release?  Thanks.

So, after a few more attempts at connecting my old project, it seems that the motor, the motor shields, and the power source are all working okay.  However, when I went back to use my new Arduino, the motors would not turn.  The program was compiling fine and running through, just the motors weren't turning.  I realized that the code on the old Arduino was uploaded with a different version of the Arduino software.  I attempted to upload newer code onto the old Arduino, and the motors no longer worked.  I think that either the drivers for the Arduino are not compatible with the Adafruit library, or the version of the Arduino software.  Does this seem like a reasonable conclusion?

I am currently attempting to power two 12V .4A stepper motors using an Arduino Mega and an Adafruit motor shield.  I had a similar setup working about 2 months ago, and everything was working fine.  Now, with this new setup, there is no power going to the stepper motors.  I have tried using two different Arduino Megas, two different motor shields, and two different motors.  Still, nothing works.  I tried powering my system from two months ago (I had changed nothing, except disconnecting a motor shield and putting it back) and that no longer worked either.  This leads me to believe that the motor shield is not working correctly, but I don't know how to check this.  I also wonder if there is something wrong with my program, but I ran the one from two months ago (that worked before) and that didn't work.  I really don't know what to do at this point, because I don't want to order yet another motor controller, build it, and have it not work.  Can someone please help with this problem?  I can provide diagrams and other information if needed.  Thanks.

I have been accurately controlling a stepper motor with the Arduino Mega and a motor shield and have been able to rotate 1 degree per step.  Recently, I changed my setup a little bit to include gears, but for some reason, the shaft of the motor now rotates 2 degrees per step.  I have not changed anything in the programming of the Arduino; I have just changed the physical setup.  Is this a known problem?  Thanks.