Yesterday, I upgraded my Ubuntu Gnome 13.04 (64-bit) virtual machine to Lubuntu 13.10. I rely on the VirtualBox Shared Folders feature to keep my git repositories in sync with bare copies on network drives at my workplace. (My Host OS is Windows 7, and my workplace IT infrastructure is Windows-based.)
To my horror, today I discovered I could not access my shared folders from my new Guest OS. I even created a “clean” new Lubuntu 13.10 guest machine, which exhibited the same issue. (Yes, I carefully performed the dance of apt-get update, upgrade, install dkms, install guest additions, and rebooting after each install.) So I knew it wasn’t an issue with the upgrade process.
Then, I remembered that the other day, I saw an Oracle announcement that VirtualBox 4.3.0 had been released. I’m running version 4.2.18. Sure enough, upgrading to the latest VirtualBox, and installing its Guest Additions solved the issue. I’m assuming there have been changes in the Linux Kernel (Ubuntu 13.10 is running the 3.11 kernel) that necessitated updates to Guest Additions.