Hi Daniel, I have the same model of DVD writer and havent had any problems with it, although I dont tend to do much else if I am burning a dvd other than maybe be on messenger.
Have you tried dropping the speed to 2x or even doing it at 1x on one of the ones that causes a problem on playback to see if that cures it ?
Maybe you could try a firmware upgrade, I havent needed to do one for mine but the 106 has been out for 18 months or more now so that may help.
I have a Yamada 6100 stand alone DVD player for my tv that plays Div/Xvid etc so I tend to burn a lot of films to CD and I have found that if I burn at 52x then I sometimes get the same problem as youre experiencing in as far that it plays on the pc fine but has problems, mainly with the audio on my yamada.
If I drop the speed to 24 x or less it seems to fix most problems.
Some media doesnt work as well as others either, especially mirrored ones give some people problems.
I am not too sure how the audio is stored on a DVD but on VCD and SVCD its usually at one end of the the film, pcs play them fine because of their greater processing power but stand alones often struggle to read from the end for the audio and from the various parts of the CD for the video content.
There are programs such as Virtual Dub and its variants which will interleave the audio with the video which can cure the problems with VCDs and SVCDs but again I dont think that the file structure of DVDs is the same, although when you open the burning programs to make a DVD there are seperate audio and video folders even though with Nero all the dvd files go into the video folder leaving the audio folder empty