Actionscript 3 :: Flash Mysterious Blinking MovieClip?

I'm creating bullets for a tank object to shoot.The tank is a child of the document class. The way I am creating the bullet is:

var bullet:Bullet = new Bullet();
(parent as MovieClip).addChild(bullet);

The bullet itself simply moves itself in a direction using code like this.x += 5; The problem is the bullets will trace for their creation and destruction at the correct times, however the bullet is sometimes not visible until half way across the screen, sometimes not at all, and sometimes for the whole traversal.Oddly removing the timer I have on bullet creation seems to solve this.The timer is implemented as such:

if(shot_timer == 0) {
shoot(); // This contains the aforementioned bullet creation method
shot_timer = 10;

My enter frame handler for the tank object controls the timer and decrements it every frame if it is greater than zero.

Bullet.as
package {
import flash.display.MovieClip;[code].......