I'll bet if you go back through your logs you'll find the singles you bought show a different MID than the ones you are having problems with now....another reason we only recommend Verbatim. If you buy Verbatim MIS that is what you'll get. Memorex/OD/Sony/Imation etc. all outsource to different companies to manufacture their media it's likely you'll actually be getting a different disc with each new spindle.