I was working on a system yesterday which appeared to be working fine. However, I noticed that when I tried to create a new page, I got this error:
Content type ‘0x01010007FF3E057FA8AB4AA42FCB67B453FFC100E214EEE741181F4E9F7ACC43278EE811’ not found in web ‘http://SharePoint:5001’.
Obviously if you are here you may have different numbers where I have ‘0x01010007FF3E057FA8AB4AA42FCB67B453FFC100E214EEE741181F4E9F7ACC43278EE811’ and a different server / farm name (although the other examples I have seen on the web had the same UID for the Content Type).
Nevertheless, running the repair option on the SharePoint Settings and Configuration Wizard made the problem disappear like dew on a hot morning. I don’t think this sort of error would be caused by a database corruption (The SaCW doesn’t do much with the DB), so it was probably related to improper security applied on one of the folders or assets in the 12 hive.
There were also some other indications out on the WWW that indicated a similar sort of problem might be experienced through an 03 to 07 SharePoint upgrade.
Thanks to Naspinski for highlighting the problem and the solution. This site may also have an answer that is more "Enterprise-Friendly" than re-running the setup, but I didn’t spot it until this morning – http://sharepointknowledgebase.blogspot.com/2009/03/content-type-0x01010007ff3e057fa8ab4aa4.html.