I had that problem often.It is usually because of syncing to sp/dif from my external reverb .If I in cubase system disables audio when I turn the sync to sp/dif on and turns off then on -then enables audio in cubase I don´t get that problem.After such a crash I close the computer then start up again after 15 sec.and run the multimedia setup and then I usually start cubase succesfully.
Kim