I believe what you're trying to do won't currently work. A few months ago I tried a similar setup (tried to setup a Linksys BEFW11S4 to talk to a WAP11) but found out that the 11S4 doesn't support the bridging option the way the WAP11s do. Supposedly this MAYbe fixed in a future firmware upgrade for the 11S4, but the Linksys guy I talked to had no idea when it would be released, and wasn't completely sure that they were going to release it.

My solution... just hook a WAP11 into my wired cable/dsl router and hook another WAP11 into the rio (using a cross-connect cable). Of course this solution is a little more expensive... Other people can suggest other vendors, Linksys is just the one that worked for me.