I decided to upgrade  VirtualBox because the newer versions have much better support for networks that allow virtual computer to be visible on the real network.

But after upgrade I encountered the error

"HostInterface': The attribute 'name' is required but missing."

It seems others have had similar issues

http://forums.virtualbox.org/viewtopic.php?p=58720&sid=f3759d4d938c30120...

I resolved this by deleting this entry:

from the config file, in my case this was

After this the virtual machine worked fine - and the new network settings are great.