A user name that contains Unicode characters is not handled correctly in Windows Vista and Windows Server 2008 during EAP authentication
On a Windows Vista-based or a Windows Server 2008-based computer, you try to establish a connection to in order to access a local network. If the user name of the user account contains Unicode characters, the connection attempt fails the Extensible Authentication Protocol (EAP) authentication. Therefore, you cannot access the local network.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB957424.