Windows – both client and server, in many versions – caches old AD-account information.
Most often, this gives problems, when a user changes their username in AD, but on another server, the old username is cached and associated with the users SID. So when a username for a given SID is requested on the other server, the old username is returned.
The reasoning behind the functionality can be found here:
The cache can be disabled by inserting DWORD 0 in registry-key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\LsaLookupCacheMaxSize
This article gives no other method to reset the cache – apart from restarting the server.
Other users have found better solutions – such as running the short 2-line PowerShell given below, which updates the cached AD-information for the given user.
$objuser = new-object system.security.principal.ntaccount “domain\<new account name>”