All you have to do is go to device manager, and right click the VirtualBox network adapter and pick “browse for driver on computer” and direct device manager driver update program to C:\program files\sun\VirtualBox and make sure sub folders is checked. If you still have network problems, reinstall VirtualBox and try to manually update the VirtualBox driver again in device Manager.
Also, check to see if your firewall is blocking Virtual Box. If it is, then unblock it or temporarily disable your firewall. You can also check your network settings for Virtual Box in your Virtual Machine settings and going to network, and make sure NAT is selected. If NAT does not work, try the other selections.