No audio - XBMC 12.3 and OSX 10.9 Mavericks

Hi,

i just installed XBMC 12.3 on my iMac 24-inch (early 2009) running with OSX 10.9.1 Mavericks.

I hear the menu sound but when i play movies or PVR, there is no audio.

Any ideas?

Thank you and Merry Christmas
Dennis