Fujitsu-Siemens Monitor problem. When using my fujitsu-siemens amilo notebook, the monitor

Question

When using my fujitsu-siemens amilo notebook, the monitor suddenly shuts down. It's not all black as you can sense a little backligt. However, only way to wake up the monitor/computer again is by shutting it all down using the power on/off button and turning it on again (which of course results in a message that windows was not shut down properly). The problem both occurs when using a programme and when no programmes are running (except for Vista). Any ideas what the problem may be?.