Two mouse pointers when disconnecting external monitor

Not an answer as such although I did inadvertently get rid of the second cursor!

I am getting the same issue - intermittently - since I upgraded from 14.04 as well.

Interestingly, the "solution" was to mouse over the image you posted! I opened it to see if it was the same issue as mine and just as I was noticing the top pointer appears to be the "active" pointer in that it changes icons as the context changes - the second pointer vanished as I moved it out of the image window!

It hasn't reoccured even though I've moved it from window to window (one of my screens is also rotated 90 degrees) and I've swapped windows. Yet to reproduce the problem but I'm bookmarking this issue to see if mousing over and then out of the image window works again!

It's a Xserver-Xorg-Video-Intel Package BUG. Fixed upstream apparently though. Still waiting for the fix to land in 14.10.