Hop pellets, there's your problem. At least on my system, the leaf hops form a nice filter on top of the false bottom, but the pellet gunk sinks right to the bottom and clogs it up. Last batch I tried to sneak a single ounce of pellets through and paid the price haha. I tried to blow it out w compressed air and succeeded in spraying wort everywhere, but failed to remove the clog. I would be interested as well to hear some better strategies for clearing a clog.