I run into this problem where I cannot access the Shared Folder in my Virtual Box. I have installed Xubuntu 11.10 on Virtual Box 4.1.4 and when I logged in after a successful installation, additional drivers was asked to install Oracle VM VirtualBox Guest Addition for Linux Module.
And so I did installed the addition on the system and hoping that I already can access the shared folder I set on Devices > Shared folders… on VM. After reboot, still shared folder can’t be accessed.
How to resolve?
To fully install Guest Additions go to Devices > Install Guest Additions from the VirtualBox menu and this will mount the VBOXADDITIONS_4.1.4_74291 on your system. Then execute the following command:
$ cd /media/VBOXADDITIONS_4.1.4_74291
$ sudo sh ./VBoxLinuxAdditions.run
You will have to reboot the guest machine to apply the changes. Then sh_Shared folder (which is the shared folder) is available under /media .