Hi folks - really need some help here. I'm currently running a; Mac Pro 4,1 (early 2009) 2.66 Ghz Quad-Core Intel Xeon 8 Gb RAM Boot ROM MP41.0081.B07 Mac OS X 10.7.2 I've just swapped out my stock GT 120 card for a new Radeon HD 5870, I have it connected to my Sony SDM-X93 monitor via DVI. On booting up, I now have NO SOUND on my Mac at all and the sound control panel states 'no output devices found'. I've also tried booting up in both Snow Leopard and Windows 7 x64 (bootcamp) but with the same results - no sound at all. All the sound controls appear 'muted'. I have read a note on Apple's site regarding a no sound issue on the MP 2009 when used with the mini display connectors but I am and will only be using the DVI port. Does anyone have any suggestions please? is the card faulty? I'm unsure as to why installing a graphics card creates issues with audio If I can't get it working it will just have to go back and I'll have to live with the GT 120 cheers all!