if someone can explain me this - ODBC

Hi! I used to connect to an SQL-Server from a Webserver on the same machine using an ODBC Data Source. This way I could make the user-authentification on NT-Basis like: odbc_connect("DSN","",""); everything worked fine until I wanted to build up a connection to an SQL-Server on a different machine.I changed absolutely nothing just the SQL-Server in the ODBC-DSN, and I got the error message: Warning: SQL error: [Microsoft][ODBC SQL Server Driver][SQL Server]Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'., SQL state 28000 in SQLConnect in ... although the $_SERVER['AUTH_USER'] contained the right user, and it was surely not 'NT AUTHORITY\ANONYMOUS LOGON' ... Where is my user gone??? And then came the most interesting part: If I accessed the .php file locally from the server (with http://servername/xxx.php ,but from the server itself), the connection has been established. IS THERE a difference, if I access the server from itself, or from another computer in the network??? Can somebody explain me all this??? Best regards, Gabor