Same here. Then I noticed it didn't creak when I stood on my pedals, only when I was sitting. Loosened seat, wiggled it around to spread the grease on the seat post, re-tightened, no more creaking noise!
2011 Jamis Quest "Cy"
2009 Trek 7500 "Diesel"
2008 Rans Stratus LE recumbent "The 'Bentley"