Oh, come on now - give me SOME credit. Of COURSE I clean the lint trap. And the vent is clear outside. What caused the problem this time was - the conduit tore at the connection to the outside vent, and there was no way to see it because it was behind the dryer. The tear caused an interruption in the air flow, and all the stuff just gathered right... there. When I replace it, I'll get a longer piece of conduit - we used this one because it came with the dryer, and they always give you just enough, but once you nip the edges once or twice, it becomes too short.