Finder error -36 with Firewire 800 but not USB

I seem to have numerous issues when copying files from my Drobo S to my MacPro (not vice versa however). I’m running OS X 10.6.2 with all the latest updates yet it I get this error consistently it seems. Only way around it seems to be to shutdown the Drobo S and hook up the USB cables. That seems to work like a charm (and oddly the speed is the same as Firewire). Any ideas why this would occur with Firewire? I’ve tried both Firewire ports on the Drobo S and the MacPro but no difference. Also, all drives are healthy, I’ve checked permissions, I’m using single redundancy and at about 50% capacity. Any help would be appreciated.

Have you tried a different FW port on your computer?
Have you tried a different FW cable?

I would also recommend running repair disk first. Error -36 indicates data corruption.