Opencores DDR2 SDRAM controller with spartan3e starter board

Ok, tried it for weeks, now I give up and ask for help...
I have a Spartan S3E starter kit board with a 46V32M16 DDR2 SDRAM on
it. My design needs to read and write 32 bit words to SDRAM. I tried
MIG 2.2 from the Xilinx coregen tools, but couldn't get it to work.
Finally I found a controller design originally written by Markus Lemke
and then modified for the Spartan S3E by David Ashley at Opencores.org
(thanks to both!). The testbench included was simulated and
synthesized fine, and works with the board as well, as far as I can
tell from the LEDs.
However, when used in my design, it fails. The design is first
writing, then reading several hundred words of data from the SDRAM.
The first word reads back ok, but all others are zero. I can see this
in the simulation as well as when stopping the clock and examining the
registers of my design.
Has anybody successfully used the Opencores DDR2 SDRAM controller on
the S3E starter board?
.