macbook pro flickering + grey screen

Hi,
yesterday, after a reboot due to a Safari update, I could login normally but, after I while, it started blinking/flickering and the color wheel appeared.
I shut it down holding down the power button but, when I powered it on again, the grey screen appeared and after a few seconds it asked me to power it down again.
I did it several times with the same result.

Any one had a similar problem? How should I proceed?

thanks in advance

grab your mac os x installation dvd in your computer while it's on.
turn your computer off.
start while holding the "C" until you get to a language selection screen.
choose you language and click the right arrow.
click on utilities in the menu bar and go to disk utilities.
select your macintosh hd in the left column and click on repair disk permisison in the right pane.
when you get that done run repair disk.

if your hard drive isn't showing in the left column then more than likely your drive is dead.

after you run the disk utilities restart you computer see if it boots. if it doesn't then start back up to the install disk and you'll have to do a archive and install.

if you need to do a archive and install start back to the install disk.
click continue through the prompts.
when you get the destination selection choose the macintosh hd then click options below.
make sure that the archive and install and preserve users and network settings is selected, click Ok.
hit continue, install.

Thank you devoult,

I did exactly what you suggested and I succeeded iin cleaning the HD and reboot... but the problem came again :
after one minute or two, the screen began flickering again as the first time and the keyboard and mouse not responding. So I shut down the computer holding the power button down and at the restart there was the same problem with the grey screen

I think it should be a serious hardware problem (the motherboard, the video card...)

Is your machine still under warranty or Apple care? If it is, make an appointment with the genius bar and take it on in to be looked at. The problem could be graphics related which would mean a logic board swap out. The flickering and freeze ups are symptoms related to the GPU.

Regards.

Yes, my machine is still under apple care protection plan, I'll call a service provider tomorrow morning (in spain)

thank you