Audio problem with H&B DX-3255

[mach]

I have a H&B MPEG 4 player model DX-3255 which I have a problem with playing audio with it.
When I play a movie the voice of the acters are misssing but I can hear the music, car sounds, shooting, etc. and some background voices, but the main characters voices are missing. I am not sure what I have done with the setup, because from the beginning it worked nicely, and now I have come across with this problem.
Can anyone help me??
thanks

[wasabiboys]

Does this happen on many discs and formats? It could just be the movie.

[Kiwi_Steve]

I have an identical problem with a Universal UNI-1708. The problem seems to occur on DVD movies with multiple language support, e.g. English & Italian tracks. Most videos with a single language track play fine, but otherwise I cannot here dialogue. I have attempted to locate a setting, but to no avail. Does anyone know of a fix to this problem?
Thanks

[mach]

Thats a rented movie so it should play properly, I have this problem since I fooled around woth the remote control to adjust some features in the setup. Yes the movies are with multiple language support, but it didnt bother me before!

[mach]

This problem does not occur with every film or formats.