First thing I would do is try copying the object and pasting it into a new scene. That will rule out whether or not your scene file is corrupt. If that doesn't do it, check to make sure you haven't done things that will prevent translation:
* no protection tag on object;
* axis locks aren't enabled in the interface (x, y, z icons) or on the object (axis arrows show the correct colors);
* the object isn't on a locked layer;
* there's no tag or Xpresso preventing movement.