I have created a slideshow and the preview plays perfectly but when I playback the final file the audio track breaks up after 22 seconds.
It could be resources of the system because it might be that the project you have is several file, each having to be read in simultaneously, if you export it out and view it with something like Windows Media Player, it should be smooth as then its one file, from one location.
The Magix software is not a playback tool, it is a edit tool... creation tool, so it has to read each file individually, each pixel, each audio sample for everything loaded. This would be more resource intense then just playing back one file.
Try lowering the output quality - or play it on a better DVD - I've experienced the same thing.
If I use the DVD players (Blu-ray and new) the damn thing breaks up.
Burn a DVD in the highest resolution and its perfect.
As John says - the older machines just can't handle your genius production!