I ran into a weird problem that I figured I would share the solution to since it seems to be floating around on the internet. Basically the scenario is that if I connect to my MSSQL Reporting Server using the IP or shortname it works fine but once I use the FQDN I get prompted for credentials and it never lets me authenticate. The root cause of this is Windows Loopback Check Functionality due to a DNS and Domain mismatch. Here's what I mean:
My Domain = domain.com
My FQDN = servere1.sub.domain.com
If you do not correctly set the "Primary DNS Suffix for this Computer" under System Properties > Change > More as seen below you will experience this issue.
If you are interested there is a MS KB http://support.microsoft.com/kb/926642 that has more details but does not necessarily address this specific cause.