Curious, What are your settings under "color Management" in the print dialog? and also, when was the last time you have calibrated your monitor?
looks like you are on a Mac (what version)
have you tried different Rendering Intent (Perceptual for example)
FWIW an update under 10.7/CS6 made my 7880 go dark similar as you describe using the same Epson profile on Premium Luster and settings -- can't recall if checking 16bit caused the problem -- i moved my printing to a 10.6 Mac Pro and haven't noticed any further problems
haven't tried printing my Epson under 10.7 since...