Problems taking pictures in the evening with the flash on. How can I fix this problem?

Tabitha, this sounds like a malfunctioning camera, and I suspect the flash has become unsynchronized with the shutter. The flash should fire precisely when the shutter is open, and this is critical timing. If the flash fires early or late, it will miss the instant that the shutter is open, and the picture will come out black. Normally, this is not a problem. But if the flash timing is off, then it may be that something has come out of adjustment inside the camera. Re-read your camera's instruction booklet to make sure you have everything set correctly. If the pictures are still coming out black, then it sounds like the camera needs to go to a factory technician to re-synchronize the flash and shutter.