you can try 10.4.11. this comes at the end of last year and fixed a lot of compatibily problems with new application, who are optimized for leopard.

i don't know what's the fast way to go back to ard 3.1. probably there is an uninstaller package, but i never used this. if you know what you have to do you can also do a reinstall or new install of osx. with a mimimum install it need's only 20 minutes on each to go back to 3.1.