Only other software I have installed are OSXFUSE/SSHFS, Tunnelblick, iTerm2, and Google Chrome. (I think OSXFUSE is the only other one besides VirtualBox that installs kernel-level code?)
I saw this after upgrading to Mavericks from Mountain Lion (where this issue did not exist—had been using ML for half a year). The system was also freezing, which was a more serious problem. I then did a clean reinstall of Mavericks, and saw this once again. I just uninstalled VirtualBox to see if the problem goes away, but I do require VirtualBox to get work done, so in any case I may just clean-reinstall Mountain Lion.
