Help with exposure on a 7D

I took the following two consecutive pics on contiuous shutter release under ambient tugsten light.  All setting were the same for both shots.  It appears the white balance or exposure has changed to make these two pics look different in color tone.  The focus point was the same for both.  I was not panning at the time.

What can cause these two to look so different?

This occured multiple times durring a continuous burst string.