Rear Driver side sounds

[downlosilvia]

I have searched the forums and found only information about wheel bearings ect causing the rear sounds. What my problem is that when i first start my car and drive it the sound isnt there, once i drive for about a mile it starts. Its sounds kinda like the brake pad is hitting the rotor, and only happens when i accelerate at 25+ mph. Then after about 2 or 3 miles the sound will go away and not come back until the next time i drive my car. Havent checked the rear brakes yet, but they seem to be working correctly. Just when i think its gone away it will start, i am not sure if the sound will become permenent, since it has only done it the last 2 times ive driven. I hope that it is not a rear bearing, i dont have time to fix that anytime soon, but it doesnt sound like that kinda of sound. I hope someone else has experienced this problem and will be able to help me try to fix it.