The virtualbox software never seemed to run properly. Boinc manager runs and it runs 12 projects at once so all seems ok.

If boinc uses virbual box, it will tell you so in the advanced view in the "status" column. It will say something like "running (8 CPUs)" or similar. It seems it uses Virtual Box always with a bunch of CPUs at once.

In the process list you can see "VBoxHeadless" as process consuming CPU time then.

If you want to see if VirtualBox is correctly detected, you can check VirtualBox Version in your profile or see in the message (also called event) log of the client. If there are errors, you can see them in the message log, too.