I've recently upgraded to Windows 7 SP1 64 bit and reinstalled my Adobe products. The clone stamp tool works correctly about 50% of the time. When it misbehaves it places the pixel data at a location approximately 5 to 10 times the current stamp diameter away from the selected location and/or smears the image in a streak the width about the same diameter of the stamp and again about 5 to 10 times the length of the diameter. If I attempt to re-stamp after undoing the damage it will sometimes work by just moving the stamp location slightly but usually requires resampling the image imformation to clone and stamp again; even then sometimes it takes a couple tryies before working. Other times it works exactly the way it should and may for the next dozen stamps before going crazy again.
I've searched the web and forum and have not found other postings of the same issue but can't believe I'm the only one with the problem. I've used Photoshop for years and never experienced this before while using Windows XP.