Was this an upgrade or a fresh install?
I could be mistaken about this being a requirement. In any event, I installed the drivers first on my Macbook running Tiger and the install was smooth. On my tower, running Leopard, it was more complicated. I think I had to use Bonjour on the tower running Leopard to see the 3800 in the OS X printer control panel. I may have confused this with installing the EpsonNet Config Utility, which you have to download separately.
Try clicking the bonjour tab in the OS X printer control panel.