Objects center & strange render problem

When I try to change the objects center location with the tools in the edit window, everything works fine. Then I go to render … and the object falls down to where the center origianally was.

example:
Pressed P to separate eyeball from head. Center origin inside eyeball. Go to test render. Eyeball falls to floor where origin origanally appearead when eyeball was seperated.Help!

is it possible that you set a keyframe for it?