I did a little more tweaking and now This Page Is Valid XHTML 1.1!
Again you have to try it with the source from a browser like Firefox, if you just point the validator at this page it renders down level which is not compliant.
I should note that the FCKeditor is only XHTML 1.0 compliant so any page with an editor will not validate against XHTML 1.1 until that support is in place. In any case since browsers seem to be forgiving I think I can still go forward with the XHTML 1.1 DOCTYPE
Also I had to fix even more content in the db where I have historically had the bad habit of using target=_blank on links to external sites. target is no longer valid in XHTML 1.1
This site is also currently using much more CSS layout and most of the table layout has been removed. I'm still working on a few areas of this and still need to update more of the built in skins to work with the new model but I figured it was good to go ahead and do the skin for this site first so I can test it in the real world.
Thanks go out to Alexander Orlov for help and good advice in working toward XHTML compliance.