I have an epson DX4850.

Mine was marking the back and I got a big cotton bud and alcohol (cd cleaning fluid OK) and cleaned the rollers. Also check that the spongy strip below the rollers is inside it's groove. Thought mine had had it, but it worked ok after this. Mine can print on linen card OK and occassionally CC's lustre card but it depends how it feels on the day.

I buy my compatibles from prink but they have to be the ones in individual blue boxes (and have to email them when I order).