Access losing links

I have an Access application with links to MySQL tables. Every time I start the application I get error messages indicating inability to read the linked tables. When I have relinked everything works fine, but eventually I log off the application and get the same problem the next time I open the application.

A similar question was posted in April 2004, but no solution that worked was posted. Exact error message is: ODBC — Connection to “GreenSheet” failed

When I defined this connection using ODBC Datasource Administrator, the test works fine.