I can confirm the same issue on Fedora with latest updates.

In my case those hangs are caused, when I enable the guest video 3D option from the VM settings...

Basically we should wait for new DRI modules for our linux distros.

I can confirm that with Fedora 20 and the latest Intel Graphics Intaller driver, everything was ok.

Then I updated to Fedora 21 and that was the problem :smileygrin: Intel still don't have the new driver installer (that include the new corresponding DRI module), so at least for me, I am stuck with this issue.