While investigating further, I poked around at other similar issues of other ODBC list issues for drivers and ran the following two commands from the command line ( taken from http://blogs.msdn.com/b/dataaccesstechnologies/archive/2011/10/19/odbc-drivers-not-visible-in-the-odbc-data-source-administrator-odbcad32-exe.aspx ) :
reg.exe DELETE "HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBCINST.INI\ODBC Drivers" /ve /f
reg.exe DELETE "HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBCINST.INI" /ve /f
It turns out that regedit has a unusual way of closing the registry key default values, causing an inconsistency in the registry.
After running these at the command line all was good.
Hope this helps others...