Well one of four possibilities ...
1) R&R
2) A dastardly Sony plot to get you to buy another camera.
3) The Minolta was jealous of the new a700 so got it's act together.
Or ....
4) ... once a month, when switching off, a Sony or Minolta dSLR will shoot a black image and look for stuck pixels to update the dead pixel map of the camera.
If you want to correct it yourself change the date in the camera menu, move it forward at least further than the next 1st day of the next month, switch off the camera