I have by accident found that someone who picked up the MM development released a new version 2 days ago! So I spent the last 5 hours configuring it – and it works now, after many restarts!
I changed the config a bit, so you might have to rebuild your stuff slightly. Most important change: All control blocks under the minecarts are now wool blocks. Old wool colors are the same all other blocks have been replaced by different color wool blocks. Also, powered rails now stop the cart if they are not powered. If they are powered, they accelerate it.\
See the Minecarts page for details please.