Cannot burn dvd with any program or any burner (Lite-On LH-20A1P)

[qanda]This thread is about the Lite-On LH-20A1P. Click here to see full specs[/qanda]I have two dvd burners, an internal and external. For almost a year they have worked perfectly to burn both data and video dvds. I’ve been using DVD Shrink and Nero 8 Ultra. About three weeks ago, I burned a couple of dvds, left the house for a couple of hours, then when I came back, I attempted to burn another dvd on my external burner and the burn failed. When I use the external burner, Nero reports that there has been a power calibration error, when I use my internal burner, it reports that there has been a write error. It has no problems with cds, it will burn both audio and data cds, but not dvds. I have called customer support at HP (my computer manufacturer), they had been restore to an earlier date, that did not work. I have uninstalled and reinstalled two different versions of Nero (7 and 8) 4 times. I have tried other burning software, to many to remember, the last one was Imgburn. The hardware appears to be fine, it will still read dvds and DVD Shrink still works, I can use them to rip to my computer, but no matter what I try, neither drive will write with any program. Please help, this problem is driving me out of my mind. Thanks