Can anyone explain or direct me to an explanation of how oracle interoperates with windows permissions?? I've been fighting datapump most of day and i'm sure i'm missing something....

I'm running windows 2003 64bit servers, i've got a few oracle 10g installs - mostly 32bit. (Version 10.2.0.1.0). I created a datapump user, gave this user rights as per metalink article 294680.1. I managed a successful export from one database but i can't get it into second database - validation error, wong password. All servers are on same domain. Using same domain admins account for the host credentials, created same user in oracle (with same rights) on both oracle servers. I've added the windows user to the ora_dba local groups on all servers. What else does oracle need before it will accept and recognise windows users???