Comment 12 for bug 1485246

The issue occurred on a fresh install of Ubuntu 15.04 but as I was previously running 14.04, you could describe it as an upgrade (though it was not through the upgrade mechanism). There was certainly a previous kernel version where this was not causing a problem, but I am unable to tell you which it was having now wiped out the previous install with the fresh install.

I will try the upstream kernel and report back. Thanks for your feedback/input.