I'll have to backup this Videohelp user's and CHa's opinions.
I noticed that when scanning medias when the burner is hot (long use, high room temperature..), I had poor results with all medias that have a "heavy" labelling. When the burner is cool, these medias give much better scans.
Like paper labels, these "heavy" company labels seem to add to the stress due to heat, now if this is from warping or from adding extra wobble or whatever else, I don't know.
Anyway RiMedia is indeed a below par brand, you never know what Ritek grade you get with these (and sadly Ritek seems to keep on selling B or even C grade discs to media companies - will they keep on doing that until Ritek's reputation is totally destroyed??). I have a friend who had similar trouble with Rimedia discs. Funny how they mimick the Ridata (genuine Ritek brand) logo, have you noticed?
If you really want Ritek discs, better stick with Traxdata. But there are many other alternatives, and with the prices drop, Verbatims and Maxells (!! made in Japan Maxells, of course) are a safer way to go...