Nios II interfering with VGA Data

There's clearly a functioning image; for some reason, however, there seem to be bands of semi-regular corruptions popping up in the final image. There are two main regions of corruptions that happen at regular spaced intervals (appears to be about every ten-fifteen pixels or so). As to the timing concerns, TimeQuest yielded an Fmax of 153 MHz- two to three times what I'm running at. I'll give your other suggestions a shot. Thanks for your help!