Okay, then the N9 end of the things goes OK, and the problem is in the PC end of things.
You are'nt by any chance running a virtual instance of Linux? In that case you need to give the virtual machine access to your USB port for mounting the N9 volumes...

Anyway, what you can do now is fix the things from a maintanance console.

• open a telnet connection to your N9; "telnet 192.168.0.15"
• mount your rootfs to the device; "mount /dev/mmcblk0p2 /mnt/2"
• check that you have /var/malf there; "ls -l /mnt/2/var/malf"
• if you do, remove it; "rm /mnt/2/var/malf"
• sync the filesystems; "sync"
• umount your root partition; "umount /mnt/2"
• log off the device "exit"

After that you can remove the USB cable and power off your device.