Why do I get that error on this piece of code:

If Bullet2(bu2).x + 30 >= StarX And Bullet2(bu2).x <= StarX + 30 And Bullet2(bu2).y + 30 >= StarY And Bullet2(bu2).y <= StarY + 30 Then HitStar2

All this code does is check for collision between a bullet and a Star shape thing I have. The error doesn't come until about 40 seconds into runtime. Please help!