Also, for what it's worth, my 360 works fine with my Airport Extreme. I can only assume it'll work fine with an Airport Express as well.
I have a feeling some of the older wireless dongles do not work. Mine is from Dec 2005, and no matter what it will not see my Airport Extreme. My 360 has all the latest dash updates so it should have updated it's firmware but still no.
Express or Extreme ?
I know my 360 can't see my Extreme, hence I kept my express to act as a bridge for the 360's wireless.
Is it that it just can't find the express at all ?