We finally got it working. Have no idea why it failed, or why it started working.
We tried reinstalling stuff. We tried changing to other targets. We were just about to uninstall the whole thing and start over and after the last reset (we must have reset the machine 10 times) it worked. So far it's stayed working.
I can only guess that it was one of those drivers where step 1 makes step 2 work after a reset, and then step 2 (only after it works) makes step 3 work after a reset...
I swear, it must have been 10 resets.