Is this Ghosting or Lens Flare?

I shot some photos at a concert with my Sony A57 and Minolta 135mm 2.8 lens and noticed all the

images had what seemed like mirror images of some of the light sources. The effect also showed

up on the video taken with the same equipment:

http://www.youtube.com/watch?v=XRnrq0g3PXo

I noticed this effect happening also on other photos shot with a light source in the picture frame and

with some other lenses.

Could I have your opinion as the cause of this, lens flare, ghosting etc and how to prevent this in

the future. Thanks.