Other than what RandQalan mentioned, are you very sure that those Verbatim discs were made by either Mitsubishi or Taiyo Yuden? Those made by CMC Magnetics are really bad.
To find out which company was the manufacturer of those discs, insert one of those discs into your computer's optical drive and view the disc's information with IMGBURN.
Unmodified SCPH-77006 with SM 3.6
SCPH-39006 with M-chip modchip, SCPH-10281 NA and refurb Seagate 80GB HDD
SCPH-10000 v1.00 with SCPH-10190 PCMCIA NA and SCPH-20400 HDD unit