HDMI out (laptop), sporadic audio problem

Iv just started using my laptop to output HDMI and iv got a problem with the audio. Iv set the laptop to output the audio and it does work, but whenever a program ends and i open up another one, or i pause it & resume it, sometimes it runs silently, despite me having changed nothing except the program/pausing.

In order to get the audio back i have to randomly unplug the HDMI cable, mute it, pause it, unmute it, unpause, chnage volume levels several times etc and eventually one of these fixes the audio issue until i pause it, or chnage program again.

Can anyone shed any light on what could be causing the audio to work sometimes and not work others?

Its a Dell Studio 1737 running Windows 7 with the drivers fully updated. It does thid with WMP, VLC and windows media centre.

Thanks in advance :)

must be a problem with win7 tbh, after all most drivers are beta

I was hoping it wouldnt be that but after 2 forums and no answers im guessing it is aswell!

thanks anyway :(