Havent come across that myself (from memory), but would suggest a service restart would resynch AD.
In SQL Server there are logins and users it probably picks up the new credentials directly from AD for login, and cannot imagine why it wants to retain the old name other than it does recognise / is cognisant of the name change.
Would be interesting to run : EXEC sp_validatelogins
And to look at : select * from sys.server_principals
In the meantime, I will have a look around to see if I can find something "concrete".