I have cruised the internet and this site looking for solutions to this issue included in the following web articles
Microsoft Post
Previous Norton Posts including
http://service1.symantec.com/SUPPORT/norton360.nsf/0/eea427af14fe222465257399006fcf04
and a post where someone suggested that all that had to be done was to go to trust control for find the XBOX 360 and change the trust settings to full trust.
I have followed all of these examples including moving xbox 360 to full trust control, locating and setting to "allow" all the programs I could find from the cited Norton post (some aren't on my machine for some reason) and then going to the firewall port settings from the Microsoft post and putting each and every one in by hand under the Advanced Settings>General Rules sub menu as noted in the Microsoft post.
Still no dice. The extender set up utility in windows media center detects the xbox 360, connects to it (after properly typing in the 8 digit security code), configures, builds a media library and then I receive an error message where the media extender claims Norton is blocking the connection between the xbox 360 and the computer. Whereupon the extender goes into failure mode and suggests I view the afore mentioned Microsoft office web page to look for a solution. (The Xbox 360 never acknowledges a connection to the computer.)
I have checked everything for compliance with previous suggestions and have no clue how to proceed from here.
BTW wouldn't it be much easier to have a feature built into the firewall system that automatically detects media extenders (especially for something as widely used as an xbox etc. and auto configure for it?) Although Norton products are not directly connected to Microsoft I, and probably a few others, would consider giving Norton a gold star if problems like this could magically disappear...