Hey I found a weird temperamental page which randomly gives me the following error
XML Parsing Error: no element found Location: http://kj2011/site_2011/nonprofit-data
That sounds like the Firefox error page that's returned when FF expects HTML and gets an empty document instead. Try looking at it with Firebug enabled and see what the Net tab says - perhaps you have a good header, but no html.
Usually that kind of thing is not due to an ASP.NET error (since with those you still have a document body for the Yellow Screen of Death page), but is more along the lines of a networking error...
Would it be possible to try looking at it from another computer to see if that's the problem?