I have exactly the same error as Vincent described. Network Analyst Messages shows two errors
"Failure while working with internal route problem instance" and "A column was specified that does not exist." There is a solution I can see the sequence, but no route. If I set the output shape to None, no error appears but still can not see the route (only for "streight line" it connects the nodes according the sequence, but that has nothing to do with roadnetwork. In the atribute table there is "OK" for all fields in "Status" column and "Null" for all "ViolatedConstrains".