I'm also hearing audio popping while using a Roku Netflix Player with a wireless setup. The noise is coming from the right speaker. It sounds similar to a computer crunching data, but is softer than the sound of the streaming movie, or tv show.
It starts when the stream begins and lasts for awhile then quiets down. I have heard the noise using both composite and component cables.
FWIW I also have a Samsung BD-P2500 that is streaming Netflix with a wired connection on another TV using HDMI and have not heard any audio popping with that setup.
For all Roku Netflix Player units affected by this I hope the audio popping will be fixed in the next firmware release, or be addressed by Roku in the near future.
Just chiming in - I have this issue as well, usually it's in the beginning stages of a stream, and becomes less or non-existent as time passes. This is on firmware 1.01 on an HDMI out directly to a TV.