Ok, after a couple hours of troubleshooting, I am getting a lot of noise from the system. Sometimes when I boot everything up, there is no noise and the motors move very smoothly, or at least, as I would expect. Other times the motor move the correct distances, but not very smoothly. The best way I can describe it is that the motors "chatter" along the rails. Also, the motor will occasionally leap into the smooth operation that I mentioned, and very quickly leap back out causing the gantry to "stutter". I have iterated through quite a bit of motor tuning to mitigate these issues with no luck, so I am thinking its something else. If I tune the motors to move very slowly (<20 in. per min) there is no stuttering or chattering, just lots of static noise. This is most likely because it is moving so slow I can notice it.
To be explicit with the questions...
A) Is it typical for the to be a lot of static noise when none of the motors aren't being utilized?
B) Why are the motors behaving as stated above?
Posted below is a video that demonstrates some of the issues. During the video the motors are not moving very smoothly and some stuttering occurs about 13 sec. into the video. (you can tell from the change in pitch of the motors).
http://www.youtube.com/watch?v=eeYtJVUH3Zc&feature=youtu.be