AirTunes keeps dropping/cutting out in iTunes 10

USUALLY, it's an issue of interference.

What NETWORK MODE is the express set up as?

Yes, unfortunatley the 'G' are not only slower... but they are getting older and a little more prone to break-down.... no thanks to the extra heat apple products pour out.

In airport utility, click on your express, then click on Manual (bottom left).

Click on Wireless tab, and what does it say in the WIRELESS MODE: dropdown...

Ok so you have it set up as a dedicated client. Which means we're already maximizing the throughput to the speakers. So, assuming it's not hardware failure, there isn't anything else we can do except to try and minimize this interference. You could try to find out whats' causing it (not always possible), or move around the positioning of your routers.... or changing the channels.

You may want to try unplugging BOTH your routers so they can re-start to see if that solves the issues. If not... you want to maybe dig in deeper and try setting your wifi manually to different channels.

Yes, an express dedicated to audio (client mode) will solve a lot of streaming issues, because it forces all its processing & throughput on just the speaker side. The downside is that joining a network as just a client won't allow your express to EXTEND the network.

Neighbours networks can compete, so can cell phones and a 100&1 other things.

What band is your express using now? The 2.4 Ghz only has 11 channels to select from (if you're on American continent), and many of these over-lap. Not to mention, they are getting more crowded by the day.

"It depends!"

A lot of routers use #1 as default.

This causes smart people to shift to channel #6, because as long as you move 5 channels across, you prevent over-lap.

This also causes even SMARTER people to move to channel #11, because they know the smart people use channel #6.

HOWEVER, the super-smarter people then shift to channel #9 now, because of what the SMART, and SMARTER people know.

And then, soon there will be super-duper-smart people on the horizon so......

Try to experiment.

It's ok, you won't see the option to change the channel in airport utility when you're joining another network. Go to the other rooter upstream and adjust the channel over there.

If your routers are part of the same network, then they are NOT completing against each other. It's when a different network starts to use similar channels that you run into problems.