That's because your Epson - and most inkjet printers, print with color inks. Subtle color problems may not be apparent with color prints. But when you want real black and white, they become really obvious. There are a couple of ways to deal with the problem. The best one is to "profile" your monitor and printer. If you haven't already profiled your monitor (alibrated it with dedicated profiling hardware and software), then the problem might actually be with your monitor. Every printer and monitor inteprets color a little differently. Profiling calibrates devices to an outside standard so that they see and reproduce color as closely as possible. There are two main companies who make profiling systems, Datacolor and x-rite. That's where I'd start.

Datacolor Web site
X-Rite Web site

We also have a color management product review section. That's whhat profiling is usually called in the broader sense, because it helps you manage and control color between devices like your camera, monitor, and printer.

Last. but not least, some inkjet printers have special black-and-white cartridges or print modes that eliminate the color inks that are causing the problem. But ultimately, the problem is a color management issue. And I think all serious digital photographers need to be doing some sort of color management - especially if you're printing at home. At the minimum, profile your computer monitor. Because if it's not right, you're never seeing the actual color of your photos.