Segmentation Fault on umount device.

I just compiled the 2.6.10.11 kernel (under slackware) on my P3 800MHz.
Almost everything works, but...

Sometimes, when I try to umount some devices (HDs) I get a Segmentation Fault error. That kind of freaks me out!!

Any idea what it could be? Something missing in the kernel?

Could it be that some proces is using the filesystem you are unmounting ?

Code:

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lsof | grep /mnt/point

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before unmounting to be sure nothing use the filesystem ?