Sony RDR-GX 120 sound and vision out of sync

hi please please help!

Ive just bought the sony rdr-gx120, and it plays and records fine, until i try and play a dvd thats been downloaded. i run the download through a program called ‘VSO Dixv to DVD’ and they play fine on my laptop and on my old dvd player, but just not on the sony one. the sound and vision is out of sync with one another, if i fast forward it for a few seconds, it corrects itself and then just goes back to being out of sync again. has anyone got any ideas why?
please help, i dont wanna have to keep my old (really old) dvd player, its to big and bulky!
dont know if ive just enough info up there for anyone to solve the problem!

thanks samantha