Recently we moved from a concept phase with AppFabric to a development phase. The concept testing had been done across several developer boxes all on the same domain on Windows 7. When we moved to an actual server, yet continued development on our boxes, those development servers exist on a different domain. Those domains are resolved in the following fashion for us, xxx-xxx.xx.xx. AppFabric had a real issue resolving this. We could ping it, we could resolve it in many different ways, yet AppFabric could not resolve the host name of xxx-xxx.xx.xx. The final resolution was to use just the server name xxx-xxx and add host entry files. This works beautifully and has allowed us to move on.
I spent days looking for answers on every search engine till I finally hunkered down and just found the resolution. It would not resolve when it was named by IP or DNS. The error I kept seeing was from the title of this blog. In the end, after reviewing and logging some serious stack trace, it looks like the .NET call to new Uri() is not able to resolve "." (dot) names. This sounds like and AppFabric bug I hope they resolve in future versions.
So if you are tracing this down and find this blog entry, and you use "." in your DNS names to cross domains, give this a try.