problem connecting to db2 with php!!!

I have already installed the apache server, php v.4.3 and the DB2 Client v.7.1. I want to
remotely connect to the database named IRO (This is the database that IPIT uses. IPIT is the name of the DNS system) I have already acquired accounts and passwords and I can execute queries successfully from the command center. The problem is that the same queries cannot be executed from within the php script. The error I get is the following:

Warning: odbc_connect(): SQL error: [IBM][CLI Driver] SQL0902C A system error (reason code = "-20475") occurred. Subsequent SQL statements cannot be processed. SQLSTATE=58005 , SQL state 58005 in SQLConnect in C:\Program Files\Apache Group\Apache2\htdocs\GRAF\EXAMPLES\odbc_connect.php on line 2 [IBM][CLI Driver] SQL0902C A system error (reason code = "-20475") occurred. Subsequent SQL statements cannot be processed. SQLSTATE=58005

The connection script I use is:
<?php
$con=odbc_connect('IPIT','username','password') or die(odbc_errormsg());
?>

Is there anything wrong with the connection string?
I am realy looking forward your help.
Thank you

Can you try a quick test, not using the command center but opening up a db2 command line and trying to connect via that interface?
i.e.
db2 connect to ipit user <username> using <password>