Loss of all sound output

[Guest Flying Low]

This weekend I installed Vito voice2go (mainly 'cos I am sad and like the idea of being told who is calling me using my own voice command) and I also had a play with the media player and the supplied headset for the first time. Now I find that after the device goes to sleep I lose all the sound. If the phone rings, there is no ring tone, if I wake it and tap the screen there is no tap sound. If I go to settings and play with the various sounds, I hear nothing. The volume control is set to max. If I do a soft reset all works well - until goes to sleep again.

Anybody got any ideas??

Barry