Front facing camera not working...

So I've only had my iPhone 4 for about 3 months now and it was working just fine until about 2 days ago when I was trying to take a self portrait with some friends and could not get the front camera to work. When you tap the flip button to change from the back camera to the front one, the screen freezes up and temporarily locks up without switching. Then after about a minute or two the picture flips only to show the last thing that was on the screen before it flipped. Then about a minute of showing you that, you can tap the flip button but nothing happens. After you close and re-open your camera, it goes back to the rear camera. When you try to open the FaceTime function, it only shows a black screen with no picture...do I need to just replace the front camera or is this a bigger issue. I don't believe the warranty is any good since I have replaced the back with an aftermarket one and would really hate to think that my phone is a lemon. I've looked all over the net and it seems like though this is an uncommon issue, no one has found a fix for it. Nothing on YouTube or even google about a fix...just people complaining about it.