DVD Burning Problems

I recently brought a DVD burner (LG 4081) with Nero Burning Suite. I made a back up disc with a DVD+RW it work fine. I also tried making some backup copies of DVD movies with DVD shrink and nero but all I made were coasters. I used DVD-R disc first and none of the worked, the computer froze soild and I had to turn it off and start again. I then tried a DVD+RW worked right away no problems. The I tried DVD+R The first one worked but the next didn’t and the computer froze again. Then I burned 4 sucessfully without any porblems. Tried a DVD+RW again computer froze reboot. This problems seems to be very inconsistant and I can’t narrow down the problem. Can some provide me with some guidence on resloving these problems. Any and all answers are greatly appreicated Thnaks.