When the light comes on like that it means that something is wrong with the system. If it was just the DSC light it would mean that it works just like when you have DSC turned off. With the brake light on along with the DSC, it could mean other things. My guess would be that one of the wheel sensors isn't working right. I will be trying to track down why my DSC is on this weekend. From what I can tell, check the wheel sensors first, but it can also be the steering angle sensor or the lateral acceleration and rotational rate sensor (which is under the left seat).
Other posts on the board suggest pulling the codes to see where the problem is. I tried to pull the codes with the key on, but the engine off. There were no codes. I'll try again tomorrow with the car running, if still no codes I'll start with the wheel sensors.