This should be pinned or something.

I had the same problem with earlier DNN 4.x release, and similar headache without understanding of what was fixed after doing all the roundabout rigmarol. In any event, a while back I worked on a SOA architecture which did a lot with loading serialized .NET objects into xslt parser, and how important all the namespaces were in properly processing the correct nodes, etc, most of which I promptly forgot when I went on to my next project.

As this was a configuration file, I didn't realy realize that it was simply being loaded into an XML document (even though I was looking right at the code) and didn't think about the namespace.

Low and behold, I removed the namespace from my web.config's configuration section, and it worked.

Thanks again for clearly spelling out your solution, and more importantly, the reason for the break.