We're having the same problem. I found out that EEPC client, once installed, modifies local machine policies in Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options.
Policy "Interactive logon: Display user information when the session is locked" is set as "Not Defined" in 32 bit win7 and as "User display name, domain and user names" in 64 bit win7.
So, I thought to set it to "Not Defined" manually in 64 bit machines (it not possible directly, you have to delete registry key called "DontDisplayLockedUserId" under "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System"), but it didn't work. Actually it seems that the system is ignoring the policy, because, even if it's configured with the other 2 options "User display name only" and "Do not display user information", the lock prompt remains the same.