The best way I have found to edit is via VBA. Make sure your cursor is
in the Query Table, and then go into the VBA Editor and hit Control-G.
The following will show you what it is, or allow you to reset it:
To fetch the connection:
? selection.querytable.connection
To change the connection:
selection.querytable.connection = "new connection string"
Also, this addin makes working the ODBC Queries via Excel much easier:
http://www.dicks-blog.com/archives/2005/11/29/query-editor-add-in/
Greg