LG FLATRON L225WS (22" Screen) goes black, but computer keeps running

Well, here's my problem:

Time to time (more or less every two weeks, or every month, it varies), my screen goes black, but PC keeps running as always; first screen on-off blue light and "Analog mode" on-screen message, then orange light and black screen (as if it was disconnected from computer, but I've revised the connections and they're alright). And after some time (10 or so reboots, only clicking computer on-off button), the screen works again, as always; then a month or so passes with the screen alright, and then I've the same problem again.

I don't think it's my video card, since just yesterday I was playing Tomb Raider: Underworld, and Assassin's Creed at highest settings, 1680x1050, DX10, and it worked fine.

My specs are as follow:

OS: Windows Vista Home Premium 6.0
HP Pavilion
Processor: Intel Core 2 Quad CPU Q8200 @ 2.33GHz (4CPUs), ~2.3GHz
Memory: 4094 MB
DX Version: DX11 (I didn't know I had DX11 until now that I've looked up system specs :confused )
NVIDIA GeForce 9600 GS Total Aprox. Memory: 2540 MB (actually I guess it should be 512 MB or so).

Well, any idea on what's going on with my screen :major?

Thanks for the help in advance !

 

What happens if you disconnect and reconnect the power cable for the monitor?

 

Intermittent problems are the hardest to troubleshoot - especially when it may be a month between events. But still, when troubleshooting display problems, it is necessary to determine if the problem is with the monitor, or with the computer/graphics solution, and the best way to do that is to swap monitors with another computer. If the problem follows your monitor to computer #2, you know the problem is with your monitor. If the problem also happens with monitor 2 on your computer, you know the problem is in your computer.

4 CPUs??? I doubt that. 4 cores, yes - even 8 with HT, but not 4 CPUs. For there to be 4 CPUs, the specialized motherboard would have 4 CPU sockets. Does yours?

Are you watching your temperatures? Is the system clean of heat trapping dust and dirt? What are your PSU specs?