You may sometimes see this error when creating a new page in a SharePoint MOSS 2007 publishing portal.
“Content type ‘0x01010007FF3E057FA8AB4AA42FCB67B453FFC100E214EEE741181F4E9F7ACC43278EE811’ not found in web ‘http://yoururl’
Two step solution:
1. Go to Central Admin, Application Management, User Permissions for Web Application.
Ensure “Use Client Integration Features” and “Use Remote Interfaces” are enabled.
2. Go to Central Admin, Application Management, Policy for Web Application.
Add your user account with Full Control and Finish!
You may have to do an IISRESET and you should be able to create new pages.