Go to Devices and select Device Setup - Then select VST Audiobay. You will see an ASIO driver dropdown menu on the left. What driver is selected there? If the MI4 driver is not selected, you need to switch that setting to the MI4 driver.

Also, here's a link to the last available driver update for the MI4 with a Pre-Intel MAC: ftp://ftp.steinberg.net/Download/Hardware/Steinberg_MI4/Mac/PPC/DriverPackage_1.2.0.0/

However, before installing this update, be sure and check to see if you have the correct MI4 driver selected in VST Audiobay.