There are two virtual buttons on each lever, one should be on when the lever is in the detent and one should be on when the lever is behind the detent. My guess is you're running it with the Control Manager installed but no map running. If so, get to the calibration screen for the Quad, either through the Game Controllers "Properties" button or through the Control Manager GUI, for the Quad and click the "Throttle Settings" tab up at the top. Widen the deadzone for that axis a bit, then click the "Apply" button. Pete mentioned it taking two buttons, probably what you've got run into is that the transition from the "in-the-detent" button to the "behind-the-detent" button is happening while you're still in the detent, probably at the back edge, and it keeps bobbling between the "in-the-detent" and the "behind-the-detent" buttons. Widening the deadzone will move that transition point further back so the lever has to come out of the detent a bit further before the transition happens and it should stabilize it. Might also help to check the calibration while you've got the applet open.
- Bob
The StickWorks
http://www.stickworks.com