Network AV not streaming media

Hi,

I have a Yamaha RX-V2065 and a Netgear stora NAS. I want to stream media from the NAS to the Yamaha but it's just appearing greyed out. The same music plays on my PS3 and the Yamaha can play music stored on my PC. It's like it's the wrong format but it works OK from the PC and I've tried saving it to the NAS as MP3 and WMA  - Any ideas anyone ?????

Thanks, Alan