How to fix - blank display; cannot sync

Here's the issue:-

My iphone 3GS LCD screen was cracked. I replaced the glass and the Home button (cable severed by accident). Everything seemed to be working fine - for a short while anyway. Inexplicably, the screen turned to a blank white screen.

When I would re-seat the cables, the phone would work and then suddenly stop working. While I was tinkering with the phone powered on (re-seating the cables 1 and 2) the LCD powered up then got a vertical white stripe from midway down and the screen went blank.

Ever since, when I try to re-seat the cables I get a blank screen. The phone has power; LCD turns to a shade of gray (backlit?) but not working; no digitizer/touch screen. I tried to install new LCD with no improvement.

So the iPhone is working; charges; rings; vibrates, powered up to gray screen; LCD is blank gray; also I cannot use slider to power down or enter pass code; iTunes recognized it on Mac computer at the Apple store.

I need to get data off of the phone. (obviously, I know my pass code - but cannot enter it on the phone or sync it while it is locked)

Is the connector faulty? Should I try to replace that? Can the display IC be swapped from a working phone? Should I try to swap my Flash memory to a working iPhone and retrieve the data? I have access to another working iPhone.

Any suggestions would be greatly appreciated.

TIA