As above, stay loose on the bike. Sounds like you have the dead sailor Going on. Hate to sound like a broken record as I recommended it in another thread earlier this morning but the Fluidride Like a Pro DVD is an excellent resource for jumping techniques.
A link to a sample clip from the DVD….
http://www.youtube.com/watch?v=yR89Umu6vt4
And a link to the site….
http://fluidride.com/2008/06/25/fluidri … pro-video/
Did wonders for my jumping (It also covers many other aspects of riding…drops, cornering, braking, etc).