If white screen sometimes goes away by closing and opening the screen, then the problem is cable connecting the computer to LCD monitor. In my Travelmate 7520 I had white screen problems, but by making sure that monitor cable is connected properly it now works perfectly. The cable was poorly connected and it moved little bit. So when it moved too much, screen went white. And when you close the lid few times it moves back just enough to start working again. It's only temporary solution, because everytime connection gets looser and looser...
Here's how to check the cable & fix white screen:
You can start by checking if monitor cable is disconnected or badly connected. In order to do this, first you have to remove plastic panel between monitor and keyboard. It's same panel which usually cover hinges and has powerbutton on it (depends on model). Carefully remove it, from right to left, start from upside of the panel. (Atleast with Travelmate 7520) Once you have removed it you should see some wires that go trough hinges to the monitor. Monitor cable is the biggest one of them, and has wide connector with many pins, usually on left side of laptop. Now you can start the laptop (if it's not on already). When computer has started, just disconnect the monitor cable, clean it, connect it again and make sure it's connected nice and tight, hopefully it starts working. If that didn't help, try to wiggle the connector and cable little bit and watch if anything happens on monitor. If not, problem might still be with the monitor cable, but at other end of the cable... That is little bit harder to test, but worth checking it before buying new LCD screen or computer. If both ends of cable are connected properly and it still wont work, problem might be with the cable itself. It's not expensive so I would buy new one and try with that before buying new LCD screen.
I hope this helps somebody, good luck.