I'm setting up a new Mac Mini running Leopard 10.5.7 with VirtualBox 3.0.0 and Windows XP SP3. This is a new, clean installation on a new system. When I installed the Windows updates (less IE8) and rebooted Windows all icons disappeared. I finally forced Windows to quit by closing the VirtualBox.
I reinstalled Windows and again installed the updates (less IE8) with the same results. I'm now in the processing of doing the third Windows install. Since my wife ( this will be her system) does not plan to use the Windows guest on the Internet I will not being installing the updates which mostly addressed security.
I really don't need a reply but am providing this as a warning to others.
Bob