the warning light comes on and i know that the middle stop light (brake light bulb is out, this is in Canada so we have the third stop light!). So i went to the dealer, got the tiny light bulb (almost $20) installed it BUT it still does't work!!!! Sooo i checked the fuse=good, checked the light bulb=good, checked if i'm getting power to the stop light=NOPE!!!
Now the question is why am i getting no power to the middle stop light (keep in mind that left and right stop lights work fine), could it be the brake light switch???

 

When I first bought my '98 S500, the lamp warning bulb would come on intermittently. I also replaced the third brake lamp bulb and had to clean off corrosion on the bulb contacts before it would work properly. Might be worth checking out on your car.

 

If it was a stop lamp switch, none of your lights would be working and you would have multiple warnings on for ESP/Bas etc. on as well. Did you get a new socket with the bulb. Chances are that the bulb melted the socket and shorted, thus causing it to pop. Try a new socket with the bulb, if that doesnt fix it, then I would bet you have a break in the wire between the fuse and light. Did you make sure the key was on when checking for power at the light, and that someone was pressing the brake pedal?