Iphone 4 screen blacks out, have to click lock/unlock button to see screen again?

It is a brand new iphone, it's been fine since I had jailbroken it with 4.3.3 software as the screen keeps going out now and again so I have to click the lock/unlock button to see the screen again.

Now it has started doing it within seconds of the screen showing, i'm guessing this could be a software issue? I'm unsure what to do.

After jailbreaking, the problem started so it may be a faulty IPSW. Although, I updated to 4.3.3 with itunes without the jailbreak and the problem continues.

It's gone from the screen occasionally fading out, to the screen fading out 1-2 seconds after hitting the lock/unlock button to the screen flashing white pressing the button

itai said:

nothing is guaranteed when jail-breaking...anything can happen.

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Could this be reversed, like installing a different version of ios?

I tried updating with itunes, the problem persists; no apple logo or visible ios screen. In fact, the screen went white when it should have been the apple logo and it flashes when I press the lock/unlock screen.

I had bought it brand new from a phone retailer from eBay, they say the warranty/guarantee isn't with them and that it is DIRECT to apple. What does this mean? Could the apple store give me a direct replacement? I was sure warranty came within the form of some sort of paper?

patp said:

if you can't get the phone back to stock OS, Apple will not replace it. If they suspect or confirm it is JB, they won't touch it.

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It has been jailbroken and I have restored it to factory settings on itunes just before, so it would be as what it was out of the box. However, the screen does not work because the LCD has fused.

Would they be able to check if it has been jailbroken since I have restored to factory settings? I mean, I have no idea if the likes of 'Cydia' is still on my menu screen because the screen does not work. Could it be detected externally?

Also, does restoring to factory settings on itunes get rid of the jailbreak?