People here must be smarter than I. How did they answer a question with so little information? Is it the low E or high? The 6th or the 1st? "Top" doesn't really mean anything. When are you trying to get the E that's giving you a D? After tuning the open string? The harmonic? If it's the low E, it's much more likely than the high E to develop intonation problems due to age.