I know you have seen this one before. I have found several answers to this problem when the SQL Server has or has had SSL Certificates on it. However, my situation differs in that the SQL Server has never had any SSL Certificates on it, HOWEVER, the client which is trying to access the SQL Server has an SSL Certificate on it, and I get the dreaded secdoclienthandshake error.
I can create an ODBC connection in ODBC administrator and test the connection and it is successful, but when I run my application which does an ADO connection, I get the error. I can run the application on my laptop (which has no SSL Certificates) and it connects just fine, but the exact same application running on the particular client gives me an error.
I have examined the registry entries for the Microsoft SQL Server clients, and only some of them refer to encryption, and they are all set to 0, however it seems that something is causing this particular client to want to connect to the SQL Server using an SSl connection.
I look forward to any responses, and am happy to supply additional information, if needed.