Strange mid 2009 macbook pro problem with NVIDIA 9600 GT

This question has also been posted in the apple forum, but nobody gave any response.
Hello!
I have a very strange issue with my macbook pro. I recently bought a second hand MBP (model no. macbookpro 5,3). With the integrated 9400 graphics, everything is fine. When I switch to the 9600GT card, logout and login, I notice a strange problem. With the power adaptor connected, everything is fine. As soon as I disconnect the adaptor and put the computer on battery, within 2 sec, the screen becomes grey and locks up. I have waited several minutes and nothing happened. Connecting the power adaptor does not correct the problem and the only option is to hard reset. 9600 GT has 512MB memory. Both graphics cards work very well in games when connected to power adaptor.

Is this graphics card (9600 GT) not compatible to be run under battery mode? Has anyone else encountered this problem?
I have to decide whether to return the laptop as defective or keep it within 7 days. So any input will be welcome.
Many thanks.

I would return it.

Could be an issue with the card or possibly the fan controller or the fan itself.
But, I'd let them figure it out on their dime, not mine.

Update to the problem...
I clean installed Snow Leopard 10.6.3 from retail disk. The problem went away. As soon as I updated to 10.6.8, the problem came back. I am wondering if my computer will always remain incompatible to any future updates, including Lion??

BTW, I took it to the Apple store, the Mac genius fiddled with the machine for a while and then told me there is a problem with the logic board. He offered to fix it for $310. If the original 10.6.3 install was working fine and the problem only occurs after 10.6.8 update, how can it be a hardware issue!

Discrete graphics safe mode

Is there a way to enable discrete graphics in macbook pro while in safe mode. Mine seems to be always in the integrated graphics mode. I want to troubleshoot discrete graphics problems in safe mode.
Thanks

There is no way to force the discrete graphics controller on when booting in safe mode. That plus other drivers, even including the sound driver, are disabled.

I would return the machine if possible. I believe like the Apple genius that it's a hardware rather than software problem. Whether or not it's related to a defective logic board, that I don't know. If you can't upgrade the OS to no higher than 10.6.3, you'll be at a disadvantage as new software is released that requires a later version of OS X.

Hi,
Thanks for the info. I realize that it is risky to keep the machine if I cannot update the OS. But I was a bit perplexed to how can it be a hardware issue if all updates up until 10.6.4 were working fine and only 10.6.5 onwards, there is this issue. If this was hardware problem, wouldn't it be happening with any OS version. What do you say?

chscag said:

There is no way to force the discrete graphics controller on when booting in safe mode. That plus other drivers, even including the sound driver, are disabled.

I would return the machine if possible. I believe like the Apple genius that it's a hardware rather than software problem. Whether or not it's related to a defective logic board, that I don't know. If you can't upgrade the OS to no higher than 10.6.3, you'll be at a disadvantage as new software is released that requires a later version of OS X.

Click to expand...

If this was hardware problem, wouldn't it be happening with any OS version. What do you say?

Click to expand...

Possibly. However, I've not seen any reports of the same thing occurring with that model MBP. And the fact that with the more powerful GPU in play and running it on battery causes the machine to lock up, points to hardware. Even if it should turn out not to have anything to do with the logic board or other hardware, why fight with it when you can return it?

Of course the decision is yours, but if it were my MBP, I would return the machine and try my luck with another.