Many, including me, has encountered the issue where a persons display name is not correct on a site (even if it iss correct in the User Profile) page. The unerlying cause of the issues is that for some reason the job that updates the user object cached in the site collection is not running at all or does'n do what it is supposed to do.
Below is how to fix "the effect" of the problem (we've not identified - yet - why the display name doesn't get updated at all) - how to force an update.
Important: This solution (as it involves deleting a person from the site collection) will cause the user to loose all priviliges and accesses. These have to be added back after the following steps are produced
- Make sure Display name in AD and SharePoint Central admin>Shared Services>user profile & properties> view user profile is same
- If Display name is not same that Click on Start full import.This imports the display name from AD to sharepoint.
- Got to top level site collection with admin priveledge
- Open the page http://servername/_layouts/people.aspx?MembershipGroupId=0 (all users in the site collection)
- Find your user, right click the name, and copy shortcut (url to the user's profile page)
- Paste the shortcut into the browser address field and append to it (don't hit enter yet): &Force=True (http://servername/_layouts/userdisp.aspx?Force=True&ID=25)
- Hit Enter
- Click on "Delete User from site collection" button on the toolbar
- Add the same user to (any group) in the Site Collection
- This time it will sync New display name from SSP
- Remove the user from the group (it's not needed anymore)
- Now the correct Display Name should appear where it should (Welcome message, Contact web part, User Picker, etc.)
Then I/we have to find out WHY the users in the site collection don't get updated as the should! :-(