Pro V8010 LCD lamp issues

Hi all,
I need a bit of advice regarding my Fujitsu laptop. It's an Amilo Pro V8010, about 18 months old.
About a week ago, whilst the laptop was plugged into the mains, the screen just went blank. The power light was still on, but seems to have no response to my input. I held down the power button till it restarted; then everything was back to normal. Odd, I thought, but didn't think much more of it.
It happened three more times.
Finally, I happened to notice that the screen was still on; I could just barely make out the display. Obivously, the LCD backlight lamp had switched off. I restarted again, and it was back to normal.
Last night, I started the laptop, and the LCD backlight will not go on at all, even after numerous reboots.
I plugged in an external monitor, and accessed all the display options in Windows; there is nothing about choosing backlight options that I could see. Then i remembered that even the Fujistsu startup screen was unlit, so I guessed it must be a hardware issue, not a Windows issue.
I fumbled my way through a black screen in the BIOS setup, but could see no options for backlighting. I also tried opening and closing the lid many times to no avail.
As the lamp switched off by itself but came back on when rebooted, my thoughts are that the bulb isn't necessarily burnt out, but a switch is broken. I searched the outer casing, and could find no switch for opening/closing the lid.
Is this a common problem? What can I do to repair it? Does it sound like a physical switching problem? Is it time for a new bulb? (The laptop itself has maybe 500 hours on it.)
Thanks for your advice.