asterisk users - Feb 2006 - White Noise on TDM22B FXO Channels (newbie)

After many days of headscratching, I finally have a TDM22B that passes 
the wctdm Freshmaker register test (fix: disable ACPI in BIOS).  In the 
meantime, I had set up an SPA-3000, and had that routing my PSTN line to 
* quite nicely.

When I move this line to an * FXO port, is works very irregularly.  
About 40% of the time, there is an ungodly blast of white noise in the 
voice stream that wouldn't go away after reloads or restarts, and 
restarts with driver reloads.  Putting one second wait at the front of 
the dialplan seemed to help, but not fix the problem.

Even when there is no white noise, the voice stream drops huge chunks of 
the voicemail prompts, rendering the channel basically unusable.

I figure there must be some zaptel/zapata configuration issue, since the 
same dialplan and PSTN line work beautifully with the SPA-3000.  I've 
fiddled with some of the echo cancellation setting to no avail.  Any 
pointers would be greatly appreciated.