I had that problem last year with my 3800. I emailed Epson tech support, and they suggested doing two or three cycles of head cleaning. I thought that was B.S., but did it anyway so I could write back to them again, and was surprised to see that it worked! Since then, I've had single-color ink spots in the print margins a couple of times, and a couple of cycles of head cleaning always fixes it. (Note that the first time I did it, a single head cleaning did *not* fix it - it took a couple more head cleanings.) Give it a try...
Lisa