We got to the point that we can see the tables, but we can't see the columns. For the record, all of the tables are called "root.". I don't know what that means in Informix speak. Based on the table names I think they are the tables that we want to see, but I'm not sure that they aren't all system tables.
FWIW, the error I see from SQL Server is: "Cannot initialize the data source object of OLE DB provider "MSDASQL" for linked server "CMS". (Microsoft SQL Server, Error 7303)"
It doesn't seem very helpful.