Comment 20 for bug 1012627

I tried on another machine with apparmor enabled where it worked until the updates were applied (including kernel update from 3.2.0-23-generic-pae to 23 to 253.2.0-25-generic-pae.

Then it began to happen - first once it worked, once not after changing several virtualbox settings (including USB support, disabling hostonlyadapters etc). But then happened again.

Finally I found the following ticket on virtualbox site:
https://www.virtualbox.org/ticket/10528

Now it works on both machines, so the reason is/was in the kernel and not apparmor or whatever other package.