It shows updates in the App Store for Garage band, iPhoto and iMovie. However, when I attempt to update them I get a message "you have updates available for other accounts" and I never used a different Apple ID.
Have you accepted the iLife applications to that came preinstalled on your mac to your current AppleID? If you sign into your account and look at the "purchased" section of the AppStore, are there applications waiting to be accepted? Then do that first, before before you try to upgrade.