I ran into this today when I was fixing up FlexWiki 2.0's RSS mechanism to work with the new security provider. I finally got the page with the links to the RSS feeds to render, and I was a bit surprised when Outlook popped up showing what was obviously an ASP.NET error message. I was even more surprised that the same URL worked just fine in IE (I'd been testing with Firefox).
A little debugging and I think I figured out what's happening. Firefox appears to be launching Outlook as the registered application for RSS documents (presumably based on the ContentType, which is text/xml). Anyway, that's fine - I use Outlook to read RSS feeds, so great. What's not great is that Outlook decided to lowercase the URL.
Hello?! URLs are case-sensitive! Who thought it was a good idea to screw with the case of URL? I mean, it's fine to write a web application that accepts either case on the server side, but you can't just send either case as a client - you have to assume case sensitivity.
FlexWiki is highly case-sensitive as part of its design. So the lowercased namespace in the URL results in a failure to look up the right information. I'd write a fix for this into FlexWiki, but frankly I'm not sure that's a good idea. Outlook seems (to me) to be pretty clearly broken on this one.
I googled (lowercase intentional) for info on this but wasn't able to turn up much. Anyone know anything?