I have a Snow iMac DV running OS 9.1, Casio CTK-601 keyboard, Roland XV-2020 synth, Edirol UM-1X midi interface and USB hub. I have tried to set up OMS but to date can't get the computer and externals to communicate. I have Local Off on the keyboard. Could someone please help this frustrated beginner? Thanks!

OK, a few pointers when it comes to OMS...
Before installing any drivers, or midi/audio sequencing programs, install OMS. This will help out more than anything else. Then install the USB and edirol drivers. Start up OMS and follow the instructions that are included in PDF. Trust me if you follow the instructions to the letter it will work. If at first you don't succeed try again! There have been many reports that running midi/OMS through a USB hub is a no go, but I have had no issues in that area. You will need to make sure that nothing else is running on the hub (printers, iPod, ect). If you do not have any luck, try plugging you edirol directly into the mac with no hub.