In case you can't fix the problems with Windows Media Center with the above mentioned instructions, this can be caused by a corrupted recording schedule recording shedule data (Recordings.xml).
You may try to
delete the following file
Code:
Users\All Users\Microsoft\eHome\Recording\Recordings.xml
Please note that it will clear all your scheduled recordings.
You can try to rename a backup of Recording.xml to Recording.xml after deleting the corrupted file.