This is not the way you want to start your evening. If you are one of the unfortunate souls who has been hit with an empty guide, hopefully this will help you get back to the awesomeness of the Media Center experience.
Backup
Wait, my guide is busted, why would I backup now? Recording Schedule! Ian Dixon, of The Digital Lifestyle has created a handy utility to backup and restore Media Center settings called mcBackup 3.0 from Made for Media Center. This utility allows for the back and restore of Scheduled Recordings, Channel Lineup, Recorded TV, Extra Folders. So, before we go any further, backup the recording schedule. I recommend this just in case things get worse before they get better.
Guide Recovery
To restore proper guide data, I had to step through the Setup TV signal wizard. The following screenshots step through the wizard. Don’t schedule the eye exam just yet, the following screenshots are a tad blurry. (Note to self: Don’t shrink Media Center so much when taking screen shots).
These configuration steps allowed Media Center to pull the proper data again. It did take a few (five) minutes for the data to populate again, but I was soon back to the wonderful state of upcoming recordings and a full grid of guide data. The following screenshot shows my guide data restored.