Hi Gavin.
I actually put one of those together from scratch, and used the driver from Aminet.
I got it to work, so as long you have the files in the correct directories, it'll work.
Either that, or a connection has come loose inside the box. If you can open it up without breaking anything, take a look.
Try downloading ppazip.lha from the internet and trying it's drivers. That disk you got might have corrupted driver files.
Good luck.