I think I'm seeing it now - since my 2009 and down serials are part of a subscription, they have been upgraded to 2013 licenses and are being lumped in when the license file is appended.
I have legacy machines running ACAD 2008, so I will need to: A. get an exception/new license from AutoDesk or B. Run the 2009 to 2006 file on a different server? Thx.
The 2009 serial number isn't valid for 2013, rather it's been upgraded multiple times to a different 2013 serial number.