VirtualBox Ubuntu Slow Shared Folders Under Windows

Often, especially with large file transfers, it seems that the shared folders facility in VirtualBox (running Ubuntu, but not sure that matters), running as a Windows guest, are very slow.

I added these lines

255.255.255.255        VBOXSVR #PRE
255.255.255.255        VBOXSRV #PRE

To this file:

\windows\system32\drivers\etc\lmhosts

And then restarted the VM. I saw a big improvement.