Ethernet streaming and occasional white noise on Windows

[AlexS]

Did a little testing.
...
So there seems to be some relation to the display turn-off but strangely that's not the whole story.
...

What are your pre-buffering and buffering settings in JRiver? What is your buffer in AIR? The values you have are probably good for debugging, but if you attempt to cure the problem, you may want to increase all of the mentioned buffers.
The problems you describe are bewildering in that the screensaver should not impact the playback to this extent, especially in the high performance mode. They say the reason the screensaver has any effect is that the CPU utilization suddenly drops/increases. But in the high performance mode the CPU should be more immune to these fluctuations. Another cure (I'm not sure how effective it is, but I have it enabled) is to give higher CPU priority to background processes than to the programs.
PS: I actually suspect that your drop-outs have to do with your NAS/JRiver interaction. My gut feeling is that there is no connection between them and the white noise problem we're discussing/debugging here. You may benefit from posting on the JRiver user forum. They've been very responsive to my questions.