I had this problem and called apple and they told me to do a full software restore. They acted like they had never heard of the problem. Well like many who have spoken up on the net, there is a real problem. After doing the software restore it did seem to improve, but then I installed my software and then the BSOD came back. I then did some more searching on the internet. I read many stories of just frustration of Apple tech support not acknowledging this iPhone 4 black screen and locking of the slider. I kept digging and came across one post that mentioned that some new protective cases that cover part of the front could be to blame. Well mine did. So I changed to another protector that did not cover any part of the front screen. I have had no Black Screen of Death problems with it so far. I will update this post if it comes back. But if you are having BSOD problems with your iPhone 4 then check it without your screen protector or case on to see if it goes away.