Check your System Library.
The templates for Magic GarageBand projects should be installed in the folder
/Library/Application Support/GarageBand/Magic GarageBand
You can go there directly by pasting the path above into the Finder's "Go" menu > "Go to Folder" textfield .
08. Roots Rock.mwand
09. Slow Blues.mwand
Are the files there?
If they are missing, try to restore them from your backup.
If they are there, but still will not open, you may have a permissions problem. Check the perinssions on the projects - you should have permissions to read this files.
If the files are truely missing, and never have worked, a part of your GarageBand installation is missing. Are all Apple Loops and Instruments there? You still may need to download the additional GarageBand contents. Try, if software update for your GarageBand version is available.