I assume you've got MOUSE X-AXIS and MOUSE Y-AXIS setup under the FSS controls (the default is OFF, so they need to be set to YAW and PITCH)?
I had to set the FSS MOUSE SENSITIVITY to max otherwise it was really slow, but it still moved.
Hmmm anyway it works OK for me! (despite occasionally having to pick up the mouse as I run out of space...) :S