DDR2 avalon bus locks up for cyclone IV

I have a design that I've ported from cyclone III to cyclone IV and I cannot get the DDR2 interface working. The design is identical. Just changed the Qsys project from cyclone III to cyclone IV and trying to read the DDR2 causes the avalon bus to freeze. (The memory chips are slightly different but that difference shouldn't affect the avalon bus.) (I've also tried removing and re-adding the ddr2 controller to get rid of a warning about ignoring the old cyclone III device.)

Is there a cyclone IV issue?