When I upgraded a couple of my PCs from Ubuntu 11.04 to 11.10 I ran into a major issue.

I live out in the country in the middle of no-where and do not have access to DSL or a Cable for broadband. I have two wireless ISPs connected to a router that has two WAN interfaces. (I am full time work from home employee so I need solid internet and VPN connectivity) The upgrade had an issue with one of the two wireless ISPs... no connectivity to the internet at all.

It turns out that Ubuntu 11.10 ships with linux kernel 3.0.0-12-generic-pae. That kernel seems to present some sort of network issue. If switch back to a previous (old) kernel like 2.6.38-11-generic-pae it works fine. I struggled to find a fix other than using the old kernel. This created a new issue when I went to upgrade version of Oracle VirtualBox because the kernel and headers did not align properly (old kernel + new heads = errors.)

I found a posting from someone that indicated one of the new release canidate kernels should resolve the problem.
http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.2-rc2-oneiric/

1. Download kernel packages for your architecture.
2. Install them using dpkg -i *.deb
3. Reboot the Ubuntu with recently installed kernel.

That resolved the network issue. Then I ran sudo /etc/init/d/vboxdrv setup and rebooted the PC. I am fully back in business with the new kernel and Oracle VirtualBox 4.1.6r74713 on Ubuntu 11.10.

I will test this for a few more days before I apply to my main PC and my wife's PC. It is appears to be working well based upon my limited testing tonight.