Can you correlate the times of the coredumps to the times that the system rebooted due to the portsnap being run?
Do you have any way to boot into single user mode and run "
fsck -y" ? If not, try running "
fsck -y" as root anyway in multi-user mode and see if it complains about any errors.
If it doesn't, you've likely stumbled upon the bug I was plagued by. The bad news: I had to newfs parts of my system to get rid of the afflicted filesystems and reinstall. The good news: the reinstall prompted me to try out KDE4, which is a pretty nice upgrade.