Also smb signing settings on the 2003 server may have caused the macs issues? ( just a thought )
The macs are OD/AD integrated so use Windows DNS, and the Sib7 server is on a windows 2008 server. Windows XP/7 machines on the same network segment hit the license server so quick you hardly notice it. Forward and backward DNS resolution is fine on the macs, routing has been checked and once the initial connection has been made it tends to connect a lot quicker.
I tried getting Avid to have a look at this, but it was a waste of breath!
1. Are you using a .local domain for your Windows network? If so, you should rename your domain to something else. That fixed us for good here. Like night and day.
2. Are you running 10.6 or 10.7/8? If 10.6 all I can see is we've seen dramatic performance improvements in 10.7 and 10.8 on our Windows network.
3. Don't use the magic triangle if you don't need to. We only have our Macs bound to the AD server. With configuration profiles you don't need an OD server. If you use something like Casper you can even apply MCX settings without an OD server as well.
The only other comment I would make is that AFP will always work better than SMB for Macs particular for searching. If you are going to use a separate storage device for the Macs than your Windows file servers, I would recommend building a FreeNAS box or buying one from ixsystems. They provide good native AFP support as well as SMB and NFS on top of a ZFS storage system. Very cost effective as well. Don't buy a cheap NAS box, they are mostly rubbish. You can build a really good FreeNAS box out of quality components for between $750-2,000 depending on how much storage and redundancy you need.