On a Mapdust-Ticket I found the bug that it don't calulates a route over the following point[1] in west-to-east direction. The point is part of a relation which says: only_straight_on ... but since the street is not oneway=yes in the oposite direction this should be no problem. But it is.

[1] http://www.openstreetmap.org/browse/node/414843507