virtualbox.org

Well that's still Launchpad and a revised version of VirtualBox. I would really be interested in knowing if the official build from VirtualBox.org works differently.
Distros use the source code and change it to suite their idea of how things should be done. I run the official builds or build my own from SVN and do not have these issues.

I installed 4.1.8 by adding

deb http://download.virtualbox.org/virtualbox/debian oneiric contrib

to /etc/apt/sources.list.

Well then I am out of ammunition. Without actually touching the unit I don't know what else to look at.
You can post the issue at bugtracker and see if the DEVs have more for you to check.
It would be great if you post a link to the ticket here so others that might have the same issue can see and add comment.

Okay, thanks for your help and advice!

I hit this same problem, unexpectedly, on a Win7 64-bit guest that's running under an old VirtualBox (3.1.8 ) which for various reasons I'm reluctant to upgrade. This solved it:

- Shut down the guest
- In the Adapter 1 (Intel PRO/1000 MT) field, change the Mac address.
- Add a second adapter (PCnet-PCI II (NAT))

I'm not sure which of those changes solved the problem yet, but it's working again.

Crazy thought, for the OP if he's still around--

Could the network switch be having issues with multiple MACs on one port?