Slow speed with shared folders in VirtualBox

I'm using VirtualBox 3 on my Ubuntu 9.04 desktop, and I've got a VM with Windows XP sp3 mapping my ~/Documents folder as a shared folder. The virtualised Windows is mapping My Documents to the shared folder directly (//vboxsvr/Documents).

The problem is that every time that I'm interacting with the shared folder (i.e.: access, list files, etc.) it takes several seconds to do so.

Is there a way to speed this up?

It seems to be an issue with name resolution. That happens on Windows machines while it tries to use the virtual network adapter to resolve the name. I have resolved this issue on a Windows host, but not on an Ubuntu host.

I found this site that has some suggestions:

In C:\WINDOWS\system32\drivers\etc\hosts change the line

127.0.0.1       localhost

by appending Vboxsvr and your computer name
so for a computer named the_box it would become

127.0.0.1       localhost Vboxsvr the_box