BenQ 1620 mysterious burning problem

I have a huge problem with my 5 month-old BenQ 1620.
I always Nero Vision 3.0 to burn my captured satTV program into DVD.
Everything runs well, and the Video runs smoothly with my Samsung DVD Player. But, all of a sudden, all my new burnt videos will only play upto about 1:20m - 1:31m in my player, then the video will freeze and the player makes some noises, as if it is having reading problem with the video data.

I have tried 4 kinds of media from DVD+RW, DVD+R Ridata, DVD+R Acer, DVD+R Verbatim and same problem, all of which I previously used for my burning needs successfully. I tried to use DVD Decrypter to locate bad data, but NONE found. However, all the discs will play nicely with WMP without a single hiccup. Now I know you must think my Samsung player gets ruined, but it is not. I tried to play all the previously burnt videos on my player (which is on exactly the same DVD+R medias), and it plays without a problem. Only the newly burnt disc will have this reading problem.

I thought it was a software problem, so I uninstalled Nero Vision 3.0, and tried Nero 7 Premium (with Nero Vision 4.0), and the problem remains. Then I tried to burn at 4x, same problem.
Then I tried to rip the newly burnt DVD (which has problem) with DVD Decrypter (which founds no errors btw), and reburn the VOB, IFO files with Ahead Nero, same problem.
Then I tried to rip the previously burnt DVD (which has NO problem) with DVD Decrypter, and reburn the VOB, IFO with Nero, same problem again. The player will always get frozen the videos somewhere between 1:20m - 1:31m. There was no indication of any problem during the burning session. It sounds like my burn quality suddenly drops to the point where DVD player can not read the data.

The funny thing is, if I force the videos to skip (accelerated play at 16-128x) with my Samsung player, the videos will finally skip the problematic areas at 1:20m - 1:31m, and will play without a problem afterwards. Why only at 1:20m - 1:31m ???

It sounds like a calibration problem ???
I have tried several firmwares, and still the problem unsolved.

What do you think ?
I really give up…completely clueless.
My BenQ 1620 has not burnt more than 30 DVDs during its 5-month life !

Make a quality scan with cdspeed to check if the burn quality is bad.