i know there is a bunch of USB extensions for OS 9, i didnt have my USB mouse connected when i installed OS 9 on my system . but it uses a PCI card for its USB.

i can hook my USB mouse up wile in OS 9 and it works fine ( also have USB overdrive installed to use the scroll wheel and other button.

i will have to check to see what all USB extensions are installed on my OS 9 and maybe that can help you to get your mouse working