Airport Express "local clock" issue?

Several questions:
Does the upgrade for the AE help its clocking?
What is Airfoil?
I just use whatever my Imac comes with to talk to the AE. When trying this, I don't know if you'd call it a dropout or not, but the music would get very 'glassy' and harsh. just for a few seconds, and not regularly. My DAC was losing lock, according to what I could find out.

Is the upgrade for me? The idea of all my CDs on confuser, wireless to stereo and a decent DAC is too good to give up!

Magfan - Airfoil is to send sound from any application (or system) to AE. Without it AE only works with Itunes. AE worked with "Front Row" with previous OS but Apple disabled it in Leopard. A lot of people wrote to them about it but they are unresponsive and Snow Leopard has the same problem.

During gap between songs Airport Express stops sending data and DAC goes to "mute" (since there is no valid signal). My Benchmark DAC1 is fast enough to come back but some other DACs extend mute to second of two of the next song. Your DAC might provide substitute clock. Play with "crossfade songs" in Itunes to remove gap.

Kij,
Thanks for answer....and more info to be stuck in my 'buffer'.
Problem with my system is NOT the 'gap' between tunes. Stereo will simply produce a glassy, nearly fingernails on chalkboard screechy sound at random thruout play.
1. happens on ALAC or MP3 at any bitrate
2. AE plugged into CA840c to be used in DAC mode.
3. Error correction at burn to confuser does NOT effect outcome.
4. Using earbuds on AE is perfect. At least for my crumby earbuds!
5. Error does not repeat at same place when replaying tune. Always at a different spot.

CA sent me the software UPGRADE which they claim (can't remember) fixes or mitigates the problem... I'm chicken since I have to connect the player to a computer, using a null-modem serial cable. Dealer? They want to CHARGE me for this 'service'.

Magfan - You can get null-modem adapter (that crosses receive and transmit lines). It is something in communication between AE and DAC. When I set my AE to the the same frequency/channel as microwave oven sound disappears after few seconds and comes back few seconds after I turn microwave oven off.. That would imply that AE has about 3s buffer. Playing ALAC should be easy on AE since it is native transmission format AFAIK.

Null modem serial cable is needed up update the CA840c player.

The AE apparently has enough built in clock instability....jitter? that the CA simply doesn't like it. I have heard a similar sheen.....a couple times, come from my DishNetwork receiver going optical to the SAME CA player.

AE to DAC null modem? on an optical line? CA player has NO USB and besides, the USB on the AE is dedicated to printer use.

I hope the DACMagic doesn't have the same....issue, or the buyers of that guy are in for a nasty surprise.

I have the correct serial null modem cable, the directions and all the goodies, but am simply CHICKEN to hook it up and 'go for it'.
If I turn my CA player into a doorstop, I'll really be pissed.