isolinux: Disk error ...

[Albretch]

Hi,
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I was testing a new box and right after running a memtest, I goot:
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isolinux: Disk error 32, AX=421F, drive 9F

boot failed: press a key to retry
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What does this isolinux error mean? Also I thought the newer versions of knoppix were using GRUB
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Thanks
lbrtchx