Hello,
I'm a french user of a MacBook Pro 17" Unibody since april 2009... And you can add another one with mine to your very long list of broken machines...
I wasn't using the 9400M for a very long time, and tonight I've decided to use it. I thinked that it was my software wich was blinking, but when I tried another one, same problem occured. Finally, I searched a topic on this problem with google, and I found yours.
Tomorrow I'm gonna take it for the whole day at work, and I will use only the 9400M, for battery life reasons. If it do it all the day, I will go to the Louvre's AppleStore tomorrow evening. I hope that they will listen to me carefully, as I worked for them some days in the past...