sound issues on xbmc

i have installed xbmc on my vu solo2 running open atv 2.0 but i have no sound on bbc iplayer and others.i have gone in to the settings menu expert but the audio output device which i inderstand should be set to hdmi is greyed out.any help would be appreciated thanks

thanks fr the reply i installed from XBMC addons plugin and then use XBMC launcher from my plugins menu if that makes sense

thanks done that still no sound from the built in media player.Should i download the kodidirect extensions?

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Fiddled with audio settings on remote all working ok now .Many thanks for your help