My 1640 w/ BSKB burns all my +R like a real champ (surpassing my 1620). But it can't seem to burn my only -R media, TDK-branded TTG02, at more than 2.4x. And even then it burns it like crap. What's the deal? SolidBurn ON (both), Overspeed ON, selected speed in NERO is 8x (what the media is rated for).