I've had that same problem in the past with a Sony DVD player. It was fixable in the DVD programing. I'm not sure what you have to work with (software) But I'm sure if you fiddle with it you'll be able to fix the problem.
I have solved the problem by buying a Denon receiver that can delay the sound by as much as 200 milliseconds. I have delayed my sound by 80ms (about three frames) and it puts the picture in sync. It seems that video projectors with line processors like the Dwin, can delay the image, thereby putting it out of sync. I think the industry is starting to realize this and more receivers are going to offer this delay feature. For example, the new Rotel coming out next month will have sound delay.
Scalers will typically delay the video about 2 frames from what I have seen. It cannot operate in real time because you need this frame plus the next to see how to de-interlace the video properly for 3:2 pulldown. Even scaling alone will likely have some delay in it as well, since it takes the processor a few milliseconds to convert the scane rates.