This may be related to the problems I have encountered trying to use the latest drivers for MSSQL:
Whilst I can create a connection via a coded DSN, I cannot via the admin interface. I also could not figure out how to edit the extension to include additional fields to either keep step with the drivers or to allow a connection string to be added like ACF does.
Thanks @martin, yes, looks to be very much related. Thanks for linking it on over. Wonder if this is a request we could submit? Seems giving a connection string field would be the way to go/track along with ACF.