I'm also having this. It started on 14.04 but has got significantly worse on the upgrade to 14.10 - it is intermittent. It would happen only occasionally on 14.04 but now happens almost all the time on 14.10. I have nVidia graphics but am using nouveau. What's particularly bad about this in my case (Sony VAIO laptop) is that when it happens my ethernet port completely stops working, it's not even detected (doesn't show up in lspci), making my laptop almost useless.
I'm also having this. It started on 14.04 but has got significantly worse on the upgrade to 14.10 - it is intermittent. It would happen only occasionally on 14.04 but now happens almost all the time on 14.10. I have nVidia graphics but am using nouveau. What's particularly bad about this in my case (Sony VAIO laptop) is that when it happens my ethernet port completely stops working, it's not even detected (doesn't show up in lspci), making my laptop almost useless.