I got this error and it showed that it was in the web.config file of my website. It took me a long time to actually realize that it was NOT THE web.config, but in a folder that Visual Studio did not show as being in the project – – a ‘vti’ folder. The text of the file wasn’t even close to xml, much less being the text from an actual web.config file.

So, if you get this error, look in the file system of your project for any vti folders which might have files in them (and the file which pops up, showing as the web.config). Delete that folder with the ‘fake’ web.config file and the problem will go away