[Aerkuld]

The only time I have driven a GT3 I'm afraid I wasn't paying too much attention to the sound the brakes made, but it must be unusual for you to mention it.
It probably isn't anything serious, but you don't really want to gamble with brakes. I'd check to see what sort of condition the pads are in. If they look OK I'd try bedding them in and see if the noise goes away. If it doesn't then I'd suggest getting them checked to ensure there are no serious problems, such as a cracked disc. It isn't something that I've heard of to be honest, anyone else care to chime in?