I met the similar case once, chroot from a livecd and rm /tmp/* reinstall linux, reinstall syslinux(my bootloader) and syslinux-install_update -iam solved that .
I met the similar case once, chroot from a livecd and rm /tmp/* reinstall linux, reinstall syslinux(my bootloader) and syslinux-install_update -iam solved that .