iPhone 4 Touch Screen Issue

Hi,

I bought an iPhone 4 off eBay last week. I bought it with a damaged screen. I replaced the screen and all seemed fine, but then i realised there was a vertical strip of the screen that would not respond to touch. Like the digitizer had gone dead down a specific strip. So i assumed the new screen was faulty and replaced it with another one but the problem remains, in exactly the same place.

I have tried restoring and DFU restoring with no avail.

Any Ideas?

Thanks
BD