Get an constant audio dropout when streaming video whilst using an external monitor (TV)

[mark_seven]

When I stream video (such as when watching Sky Go) I like to connect my laptop (HP Pavilion dv9000 / windows vista) to my panasonic vieira tv with a HDMI cable - as obviously it makes for a better viewing experience.

I have been doing this for 6 months+ with no real problem but in the last few weeks I've had a constant audio dropout - by which I mean the video sound, which is being played through the tv, goes off and stays off for a couple of minutes unless I refresh or exit full-screen mode. This will happen again after a few minutes though and becomes very irritating. There is no problem with the picture though- that continues to play unaffected.

If I return the audio to playing through my laptop again then there is no problem - this isn't really a solution for me though.

The only recent software change of note was that a few weeks ago Sky Go (formerly Sky Player) requested I update MS Silverlight to the latest version - which I did. I have no idea whether this could have had any effect on the audio streaming. 

Any help would be appreciated. I realise this isn't forced to be a HP problem but if someone on here with a knowledge of this kind of stuff could help it would be much appreciated.