I bought these DVD+rs that have a max speed of 4x... but for some reason I can only burn them on 6x or 8x which seems to be making every dvd i burn have issues with video playback. Its not the burner i dont think because I can burn 4x on other dvd+rs. I dont know why these wont burn at the speed they are supposed to... Any ideas to fix this problem to get it to burn correctly?