To free the camera, select it and go to thw Object menu, click on "Constraints" and seelct "Clear constraints". It will move freely. You will lose the "Autotrack" constraint but you can easily add it and continue from there. Just FYI, if you add a follow constraints that modifier will take over.
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Paolo Ciccone
Pret-A-3D
http://www.preta3d.com
http://www.paolociccone.com