Treadmill use question-

I recently purchased a treadmill and I'm loving not having to walk out in the cold. Prior to the treadmill coming I was walking four miles every other day so I'm in pretty good shape, not over weight, and have no health problems. I use the treadmill about 45 minutes daily and have no problem walking or jogging when on it. My problem is when it stops- my world spins and I feel VERY nauseous. It is if my equilibrium is totally out of wack and stays that way for a good hour. I do a long cool down and that doesn't seem to help I also make sure I'm hydrated and have food in my system. Again, I'm fine while I'm on the treadmill but the minute it stops 'oh boy!' my world spins. Anyone have any insight? If this continues I will not be able to use it anymore as I can't stand this feeling. Thanks-Kristi