Just bought my Sony A230 a few weeks ago and I'm having this problem.
This long "dust" particles keeps reappearing and disappearing from my photos. And at all occasion, it appears at the same place, but shifting side to side.
Got an example here -> http://www.flickr.com/photos/ahmad0420/4437666781/ (It's seen on the top right of the photo.
Went to Sony Style at Paragon to "blow" it away, it went away for a while till it reappears again.
If its the dust in the sensor, why does it keep appearing at the same place? Or is it somewhere else?