Seems we have a nasty little bug where if you use a cart to travel through a Mystcraft portal you will get a nasty little crash.
So setting up those nice lava runs from the Nether to your Homebase is not a possibilty at this point.
Not sure if its a mystcraft thing, railcraft thing.. (should not be the cart is minecraft object) or a forge thing.
Can't update to the newest forge because they seem to be down. But the current forge used in DWP it will happen.. And happen bad.