I found the solution, you have to reset the screen resolution on the PS3 itself by holding down the power button when u turn on the PS3. Thanks for the suggestions
dark_ruffoWith the PS3 powered off, hold down the power button until you hear two beeps, then release the button and the image settings of the PS3 will go back to default settings and it'll ask to reconfigure resolution, video output and stuff.
Maybe that will force GT5 into 2D again.