Just to get back about how the upgrade went from 3.1 to 4.0.
*In the words of Borat* "Great Success!"
Was real easy, just changed the apt sources to etch and the amd64 packages updated as well, even though there was no config needed in apt to select amd64.
Rebooted, reinstalled ISPC, found mysql 4.1 was not available for debian 4.0, had to upgrade to 5.0, removed and purged the config packages for mysqlclient and libraries for 4.1.
Had to then recompile ISPC again as it was using the 4.1client libraries. After that tested everything, it all works.
Thanks for the help guys.