I just run into the same problem and I started doubting about the printable issue.
I have an LG 4160B and I burned RIDATA/RITEKG04 media with it (and with the previous burner) for almost one year without problems.
I don't have a printer to print on DVD's, but one friend of mine with the same burner has such a printer and started to have reading problems with movies burnt on printable media, and, just like you, even before printing on them (so it's not a printer problem).
He passed me some of his blank printable media (some Prodisc S04 and some Ritek G05) and I could NOT get a single good-reading DVD. Movie always hangs at some point (different movies, all reading perfectly on non-printable media by Memorex, Verbatim or Ritek).
I don't have the same exact media (Prodisc S04 or Ritek G05) as non-printable, to make complete test, but it's odd that only those printable media are giving errors on both burners...
I also suspect that the media companies treat the printable ones as "low grade" stuff.