Well I don't have any wrong structures as far as I can tell.
When I use firebug in firefox I get the following error:
EDIT: I just discovered that there are problems when using the non-breaking space " " (which corresponds to " "). Getting rid of those seems to help a bit... I'm still getting "Encoding error" problems, I have no idea what is causing them, I'm looking into it...
EDIT 2: I just discovered that some entities need to be double encoded (maybe when within attributes?), so "&" becomes "&" and " " becomes " ". That took care of the "encoding error" issues.
However I still get the INVALID_STATE_ERR referred to jquery and also to ckeditor. In ckeditor.js it refers to line 54, that has exactly to do with processing nbsp's and "\xa0". So I have a hunch it may very well have to do with that...
John R. D'Orazio