Can’t bind to AD

I try to bind a 10.4.11 eMac to AD and I get an error that it can’t find the container. It says it doesn’t exist. IT DOES!! This works fine in my test environment. The difference I see (and I’m no AD expert) is that the test system has an AD created/configured in a Windows 2003 Mixed functional level and my production AD is in a native functional level. Can this be my problem? I’m using 10.5 server on the Apple side. Also, I have a MacBook with 10.5 client and the bind works great. Help please!!! I need this fixed in a week for my school district.