This seems to be a common problem for both Windows & Mac users. Formerly printable dark areas collapsing into black is the typical complaint, and the worst examples seem to be with RC and glossy papers. May be related to CS4 or the Epson drivers, although I think I had this problem back in CS3.
My solution was to carry a global Curves adjustment layer at the top of the stack which caused the dark areas to be squashed down. It forced me to open up the dark areas in post. When I went to print, I would first disable this layer. Really stupid technique but it worked, probably at the cost of some slight loss of print quality. I also tried adjusting my screen gamma to 2.7, that sorta worked but it was an oppressive looking place to hang out.
Finally I got my own print profiling system (Spyder 3 Print). Whatever the problem, that either fixed it or worked around it. In any case I should have done it much sooner.
Edit...I'm sure you've done it, but sometimes when going to a new profile one forgets to adjust the Media type. The media type setting has a much more profound influence on print quality than the profile, I still don't quite understand why Epson buries the media type selection down in a normally not-visible sub menu.