virtualbox.org

Hello everyone,
I have a windows XP SP3 installation,and i currently running a Ubuntu 12.04 Guest.
With recent updates of VirtualBox 4.2.x,4.3.x i cannot share folders in Ubuntu.
Following the standard procedure wich is decribed in Help Files
i always get the following error message:

mount: wrong fs type, bad option, bad superblock on 1,
missing codepage or helper program, or other error
(for several filesystems (e.g. nfs, cifs) you might
need a /sbin/mount.<type> helper program)
In some cases useful info is found in syslog - try
dmesg | tail or so

I tried almost everything workarounds i could possibly found on google.
is there something that i'm missing?
should i downgrade the guest additions(and virtualbox version)?
thanks in advance.