I've just replaced the screen and digitizer on my iPhone 3G they came as one item together don't know if this is how it is always but anyway... It now starts up showing the apple logo then after that the screen goes White and stops when plugged in to my laptop it doesn't even acknowledge anything is plugged in. I have held the two buttons in for a few seconds and it turns off, I can then turn it on an the same thing happens or plug it in to the laptop which automatically turns it on an the same thing again, I think it must be charging through the laptop though because the battery was dead beforehand. Is this a faulty screen I've bought or is there anything I should do. Also I struggled sliding the ribbon into clip, the other push on clips was easy so could i have damaged this ribbon sliding it in? (sorry I can't tell you the numbers I think the screen had been replaced previously as it wasn't numbered)

Have you tried a restore?

Also see if you can get a copy of the syslog/console output. It can often show why the boot failed.