Logonuser on windows 8 and windows server 2008 doesnt work

Im trying to use this function to access our domain. It works perfectly fine on windows xp ans windows server 2003. Any solution for this? Im using windows 8 as my test machine and my server is windows 2008
[DllImport("advapi32.dll")] private static extern int LogonUser(String lpszUserName, String lpszDomain, String lpszPassword, int dwLogonType, int dwLogonProvider, ref IntPtr phToken);