Iphone 4 stuck on black screen? - 1

Well I locked my phone and when I went to bring it back it turned out that it ended up staying on a black screen. ITunes still recognizes it but I can't get anything to show. It was on near full battery when it went and I can't use the lock button (it's been stuck for a while). What can I do to fix this?

Also my phone is jailbroken and I'd rather not lose my jailbreak so what can I do to get my phone to work again without losing the jailbreak.

If you have droped the phone it could be that the flex cables may disconnected but if this is not the problem then you may want to reset it with your pc but first backup you files then proceed.