Most auditoriums and theaters are dimly lit as well. If your aperture is wide open at f4, and your shutter speed is slower than 1/60 of a second, you're most likely going to get blur.
Without having a lense capable of f1.4, 1.8, 2 or 2.8, you won't have access to a faster shutter speed.
The only thing you can do is crank up the ISO. This will introduce more grain into your shot, but at least it'll be in focus, and allow you to get the picture. There should be a setting in your camera that allows you to turn on auto ISO, I recommend it highly, in your case. The next time you're in a dark audiotorium, set your camera to shutter priority, adjust the speed to 1/80 or faster, and both your aperture and ISO will set themselves in a position to where you can get the shot at 1/80.
Auto ISO is nice because it allows you in a pinch to whip out the camera, set your shutter speed or aperture according to the conditions quickly, and get a non blurry shot. Maybe you're on a dimly lit trail and see an owl or deer, and you only have seconds to get a picture. It's a blessing in situations like that. However, make sure you learn the relationships between the shutter/aperture/iso by experimenting. Leaving everything on auto is a good way to never learn, if you take it for granted. :)
Be warned that this point, you're really at the limitations of the lense in that situation. You might want to consider an upgrade, but when you start looking at lenses, this is where the hobby *really* gets expensive. Learn the relationships like the back of your hand first, and you'll instantly know when you've run into that wall when you get there. :D
