Firewire issue unsolved

Hello, I have an iMac 10.6.4. I have been trying with no success to hook up (via firewire) to the Alesis Multimix 8. I also have the Tascam 1804. I downloaded the correct drivers for each source. Followed all directions such as turning units off and restarting. For some reason, it seems the iMac does not see either of the units. I have been alternating the units several times, removing and re-installing the drivers. Yet, I cannot see the either unit in hardware overview, nor in Logic Express. I am using a new firewire 9 pin to 6 pin cable. When I click on the icon for the Alesis unit, I get a message saying "Alesis Firwire, no devices found, connect devices" The Alesis does not show in Logic Express either. As far as the Tascam is concerned, their message states, FW1804 not available. It seems the iMac just does not recognize any of these units. Can anyone shed light on this for me please, I would hate to run out an buy another interface!

I noticed the driver for the 1804 was for Snow Leopard 32bit only. Would that make a difference in Snow Leopard?