Small glitch: if there is unit with unique flag, which is on production list but such unit already exists, following message appears:
can't build Unit from the list; reason unknown! Postponing...
Can't build unit, reason unknown
Can't build unit, reason unknown
Augmented2 ruleset/modpack for freeciv2.6: http://forum.freeciv.org/f/viewtopic.php?f=11&t=91047