I put some CRC Brake Disc quiet (pink goo) on my brakes to help make thme quieter (Hawk HP+ pads front and brake). Not only does the **** not work but now sometimes when I have had the car parked for a little while when I start it up and put it in reverse there is this loud rubbing sound comming from the rear. Must be something with the pads; any ideas?

I am going to have the brakes redone at a reputable service place, but wanted to see first if you guys have any ideas.