>>>It may. But the ODBC has not been changed; something else changed. And then the ODBC stopped connecting to the SQL s

Embolded: Speaking of driver file itself ? Or all settings ?
Why? AFAIR there is/was an option in connection strings as well to influence "defaults" to the setting used to establish the connection.
Probably "only" changes "access" keys in the registry, not any setting of/"inside" the SQL server installation, but I never looked in detail.
And changes made in the registry (which subkeys to load automagically) might influence your connection as well...

>>Check your ODBC driver's documentataion (ha! you don't know where it is! - neither do I), there may be just another clause to add to the connectstring to make this work.

One place to start might be connectionstring.com

regards
thomas