The wireless access point in our Linksys WRT54GS stopped working. The wired router still is working fine. I switched the Airport Express from using WDS to directly connecting it to the router.
This makes me think that it is better to use a seperate wireless access point and router, instead of integrated one. In addition to being able handle a failure in one of these pieces, it will allow easier upgrading to new wireless or wired protocols when they are available.