I finally solved the Airport Express problem I’ve had since I got it. The Airport Express would simply “drop-out” for a second or more. This wasn’t that noticeable when streaming music since iTunes buffers so much that a short loss of network connectivity had no effect. But when I used it to set up our temporary office, the drops were much more noticeable since I live in ssh sessions to various servers.
After lots of trial and error, I simply unplugged our older Linksys access point. It’s an 802.11b access point and the Express was getting confused between it and the newer 802.11g access point also in the house. Not a single dropped connection since! Fortunately, it doesn’t appear that we need the 802.11b since the greater range of the 802.11g access point seems to cover the house.