Windows Vista Vista Home premium keeps 'auto muting'

Toshiba Satellite laptop keeps 'muting the volume' - any ideas why?

I have it set up with a Hawkings USB skype phone.

The sound system is defaulted to this for both mike and speakers.

Ocasionally, when I am browsing the net for instance, I will notice that the speaker icon shows muted.

Sometimes, if I leave the laptop for any length of time, when I return and touch the mouse to wake up from the screen saver, the volume icon in the taskbar shows muted.

I'm sure it's not me inadvertantly catching the Toshiba 'quick keys' (FN Esc).

 

Thanks Steve - not that. All six root hubs have power management enable boxes unticked.

Dave

PS - I have discovered that 'auto muting' always seems to happen when 'awoken' after sleep / standby / hibernate?