Don't know if this is still an issue, but I've got some mouse-controlled camera code here which works well. you'll need to define all the variables as int:
public boolean mouseDown(Event e, int x, int y){
lastx=x;
lasty=y;
return true;
}
public boolean mouseDrag(Event e, int x, int y){
//look left/right with mouse
camera.rotateAxis(camera.getBack().getYAxis(), (x-lastx)*TURN_SPEED);
playerDirection.rotateY((x-lastx)*TURN_SPEED);
//look up/down with mouse
camera.rotateX(-(y-lasty)*TURN_SPEED);
lastx=x;
lasty=y;
return true;
}