See also bug 4660. The info message in node_scheduler.c "%s: job %u never runnable in partition %s" would be more helpful if it said why. Leaving this one open to some discussion - the answer to this bug might be simply to turn up the debug level, or there might be an elegant way to make this message or the error message "Requested node configuration is not available" a little more helpful.
*** Ticket 15446 has been marked as a duplicate of this ticket. ***