I use virtualbox 4.1.14 directly from the developers including the extension (not the ppa) on an ubuntu 11.10 system.
I try to access the internet from the kubuntu live cd that I have booted inside the VM. I think the external environments shouldn't play such a big role for the VM. I chose NAT for Adapter 1, "Intel Pro/1000 MT Server (82545EM)" as someone on the net recommended that.
I tried it with DHCP within kubuntu. Since kubuntu showed that it had no IP address, I also tried it manually and by executing dhclient manually. Using these two ways, I got local IPs, but I am not sure what the right settings for static IPs for the virtual machine are.
When I try to reach www.google.com in rekonq, the site is not available, although rekonq "loads" several seconds. I also tried to replace the DNS server by the IP of my router/IAD.
Even when I ping google's IP from within the virtual machine, "the destination host is unreachable".