Q: Screen stuck on Grey apple on black background with backlight permanently on, no LCI

I would be really grateful for some help in mending my 15 month old iphone 4S please!

I had never had any problems with the phone until last week. It had been at around 80% battery and, on picking it up, I was surprised to see that the screen was black and that it appeared to be off. It looked like it had run out of battery so I plugged it in to recharge.

On charging, the screen just shows a black background and grey apple and the backlight is permanently on. So I have tried/checked 3 things:

1) I have tried pressing home and power and then home, but the same screen returns.

2) I have plugged it into itunes for a restore/recovery. I thought it was going to work as the itunes connection picture appeared on the phone. Itunes then went through its restore process but at the end it came up with error 4005. 'The phone could not be restored. An unknown error occurred.' I do have the latest itunes installed and am at a loss as to know what to do next.

3) I have looked to see if water has got in but the Liquid Contact Indicator is not on.

If anyone has any ideas on how to go forward, I would be very grateful!

Kind regards and thanks

Shirley