I think I have now identified the issue here is related to the use of portals. On the layout I have included a portal which has a multi-criteria relationship (shows all records - although this is not particularly long at this stage). I removed this and the problem was resolved. I have now changed this to a relationship based on more specific criteria which displays a much shorter number of records. This seems to work effectively. I did note in the ODBC/JDBC pdf - Chapter 7 Supporting Standards, it says the SQL driver does not support FM portals. My guess is that the MySQL driver may have some issues with multi-criteria relationship setting but I may be wrong.