SmartRipper? Sure it's old, but it has proved to be able to handle some discs newer rippers have choked on.
Also, if you have enough space, try making an image of the DVDs using
ImgBurn (yes, it is the continuation of DVD Decrypter's burner, which is why it looks familiar), then use
Daemon Tools to mount it and attempt to use the rip tools on the mounted image rather than wrangling with the DVD drive. Alternately, you could copy the disc's contents to a folder and then just point your ripping program at the folder rather than at the drive (SmartRipper allows you to do this, dunno how many of the others do though).
I actually have a LITE-ON SOHW-16
93S, although I don't have any of the DVDs in question. If the 1673S is older than the drive I have, then your drive may be the one to blame here (specifically, the fact these things are 3½-4 years old). Mine can't even burn discs anymore, although it can still read most of them. I recently had problems with it trying to read a Verbatim DVD+R DL (MKM-001-00, for the curious).