XBox Media Center Connection Troubleshooting

My Xbox used to work well as a Media Center Extender (streaming TV to my Xbox) but since I installed Win8 on the server it regularly fails to connect. I have found I need to remove the certificate and re-add the extender to get it to work:
Here are the instructions from:

Windows Media Centre | Xbox 360 Console | Set Up Windows Media Centre on Xbox 360 - Xbox.com

• Click Start, type mmc in the Start Search box and then press Enter. If you are prompted for an administrator password or for confirmation, type the password or click Continue.
• On the File menu, click Add/Remove Snap-in.
• Click Certificates, and then click Add.
• Select Computer account, and then click Next.
• Select Local computer, and then click Finish.
• Click OK.
• In the Navigation Pane under Console Root, expand Certificates, expand Personal, and then click Certificates.
• Right-click Microsoft Windows Media Center Extender Host, and then click Delete.
• After you remove the certificate, uninstall the Extender and then restart Extender Setup.