BeagleBoard ASOC problems

I'm having some problems with alsa output on a beagleboard (rev b5) with current linux-omap git sources, plus a copy of the overo omap3/twl4030 config.

- When the device is initially opened and playback started I get a high pitched tone that lasts about a second.

- About 5 seconds after stopping playback and closing the device I get an audible "pop".

Once started, playback works fine. Stopping then quickly restarting playback works fine. It's only when the device is left idle for several seconds that artifacts occur.

Any suggestions?

Paul