iDVD is not a part of Mac OS X operating system but a standalone application that works with Mac's DVD drive to record projects onto a DVD-R disc. If you are facing issue, where every time you open iDVD application and can’t find existing projects then just follow the steps mentioned below.
Note: Below mentioned steps can also be followed in case iDVD application freezes.
Step 1: You need to delete iDVD pref file. Go to your Home folder/Library/Preferences/com.apple.idvd.plist. Drag plist file to the trash.
Step 2: Now restart iDVD. After opening application, try signing in from new account.
Step 3: Still if you are facing issue then you need to uninstall the iDVD app and re-install it again.