Before yesterday I was running the latest ISE on my machine, but I did reinstall it cuss of other problems. Now I had the same problem as Graham.
With the latest version it was working fine with ED 32 Bit. But not the 64 Bit nor Horizons 64 Bit.
I also uninstalled the newest version of ISE, and installed the 1.0.2, and now its working out of the box like a charm.
So glad I found this topic. Though I do wonder why on my previous install everything was fine. But on my current install it was doing crazy things 😛