What is the change?
In Spring ‘10, when you create a new custom object, the “Read,” “Create,” “Edit,” “Delete,” “View All,” and “Modify All” permissions for that object will be disabled by default. After the Spring ’10 release, you must specify which users should get access to custom objects.

Note: You can only change the object permissions for custom profiles, not standard profiles. As a result, users with standard profiles (except System Administrator) will not be able to access custom objects created after the Spring ’10 release.

How will this change impact me?
If you have users assigned to standard profiles, clone these profiles and reassign your users to the newly created profiles. Then, when you create a new custom object, you will edit the user profiles to enable object permissions. Additionally, you can use enhanced profile management to edit multiple profiles at once.

Note: For custom objects created before the Spring ’10 release, access to these objects will not change. Therefore, standard profiles will continue to have access to custom objects created prior to the Spring ’10 release.

When is this change taking place?
This change will be made with the Spring ‘10 release. Please check http://trust.salesforce.com/trust/status/#maint to understand when your instance will be upgraded.