Office 2007 client can't authenticate to IIS/SharePoint when opening Office 2003 documents

We just did a domain migration (name changed) where I work. It was recommended to us by our consultants that when it came to SharePoint, the best course of action would be to create a brand new SharePoint server on a different machine in the new domain rather than attempting to migrate the current SharePoint to the new domain. (At this point, I'm fully of the mind that this was bogus advice......)

I set up the new server identical to the old server.  I created a new farm on the new server. I detached the content database from the old SharePoint web application and re-attached it to the new SharePoint web application.  Everything appears to work fine.  All sites are intact, I can run reports and open, check-out/in, edit documents directly from SharePoint, etc.  

The issue is:  Users who have Office 2007 or higher installed on their desktop cannot open Office 2003 documents from a UNC shortcut.  They can open Office 2007 & higher documents.  Users who have Office 2003 installed on their desktop cannot open Office 2007 & higher documents from a UNC shortcut.  They can, however, open Office 2003 documents.   Everyone can open the documents directly from SharePoint, the problem occurs when trying to open them from a shortcut folder. (UNC path = "\\servername\davWWWRoot\site\sitefolder"). 

The error that they get is "\\servername\site\document.doc" cannot be opened. Has it be moved, renamed, or deleted?.

In looking at the ULS logs and looking at the Failed Request Tracing Logs for the site, I can see that when an Office 2007 client opens an Office 2003 document from the shortcut, a 401.2 error occurs. From what I understand, this basically means that SharePoint and IIS cannot agree on an authentication protocol.  I verified that both IIS and SharePoint are using the same authentication protocols (even identical to the original server, which still works if I turn the site back on).

I've googled and tried every viable fix mentioned. I've been fighting this for 2 weeks now.  I created a second site collection on this same new web application. Lo and behold, this second site collection works fine. I can access all documents via the shortcut without issue.  This second site collection obviously uses the same SharePoint & IIS and the same content database. I've enabled all the same features on it.  

Any and all help would be appreciated.  

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I have listed below some of the methods/fixes that I have tried that have failed. (I've tried a lot more but at the moment can't remember them all)

• Made sure the Windows Server 2008 R2, SQL Server 2012, and SharePoint Foundation 2010 w/SP1 were all the exact same version on the new server as they were on the old server.
• Made sure all of my farm settings and site collection settings are identical on the new server to the old server.
• Turned off the "Automatically detect settings" in IE.
• Made the site a Trusted Site in IE.
• Made the site a Trusted Location in Office.
• Turned off the Protected View settings in Office.
• Did a repair on my Office (I'm using 2013 but have access to 2007 and 2003 for testing).
• Completely wiped my laptop (I needed to install Windows 8.1 on it anyhow) - I did a full wipe of the hard drive (completely reformatted it) and installed Windows 8.1 fresh. Just to be sure that I could eliminate whether it was due to profile issues from the user migration to the new domain and/or document cache issues and/or client side office issues, etc. (We are still working through some My Documents redirection & user profile issues from our migration).
• Verified that all authentication settings in SharePoint were set correctly and identical to the original SharePoint server.
• Verified that all IIS settings in the new server were set correctly and identical to the original server.

Sincerely Frustrated :(