No, I have the same problem playing .wma files using WMP11 as the media server. WMA files play from the DSM-G600 and the PC. Both with the same problem. As I mentioned earlier I have ripped the CD collection to .wav files and they are playing from a usb drive attached to the DSM-G600 just fine using the DSM-G600 as the media server. No problems so far and I have played hours of .wav files.
I was not aware that .wma files are not supported by the DSM-G600 media server. What audio formats are supported by the DSM-G600 media server?