Internet works perfectly on host (Ubuntu 13.04, 32 bit, fully updated) but cannot connect to internet on guest Windows 7 (under Virtualbox 4.2). Have tried NAT and Bridge Network - none worked. I had internet connection in the guest OS a couple of months ago, but I haven't tried the virtualbox since and now it's gone for some reason. I would be grateful if someone could help me re-connect the windows OS back online (without the need to format my computer or to uninstall and re-install the guest OS). Thanks!
I was having the same problem on Ubuntu 12.10 64bit using Virtualbox 4.2.22. Here are the steps I took to solve my problem:
At that point you should be able to start a web browser in your VM and get a connection. This video provided the information I listed above even though it was used on a Windows 7 host with a Windows Server guest.
Here is an image showing an example of the settings you need (taken from this answer):