Before installing a new driver you first must trash the old driver files. On the Mac, the files do not override the old files. Trash the following driver files located in the Epson folder in the Extensions folder:
Epson Monitor 2
Epson Stylus EX
Rebuild your desktop and install the updated driver with extensions off.
Carmine notes that he could not find this recommendation anywhere in their online FAQs or the accompanying driver documentation. In any case, it did work for him.
Update: Tom Ritch and Tom Hensley followed the above advice but had no success in eliminating the problems they were having (such as printing from FileMaker Pro) with the latest updates.