OK. You need to install the jessie-backports verison of the Intel driver in order for it to work in Debian 8.
See my post here where I solved it: https://groups.google.com/forum/#!topic/qubes-users/BJRnCNcDtoo -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To post to this group, send email to firstname.lastname@example.org. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/88c5921d-c26f-4b8f-a8d5-82226611bd18%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.