As you can read on http://amailbox.org/mailarchive/linux-netdev/2010/10/23/6288128/thread VBox stops working with bridged Networking and TAP devices since 2.6.36. Reproducible: Always Steps to Reproduce: Howto create tap-interface: http://www.virtualbox.org/wiki/Advanced_Networking_Linux
Created attachment 252595 [details] All files in app-emulation/virtualbox-modules I added a modified ebuild to my overlay which includes the patch from http://www.virtualbox.org/ticket/7649
This should be fixed in 3.2.12