This fixed the huge mouse pointer problem for me: enter Coherence mode, and then exit Coherence mode.
Note that in general, if I move between using my Thunderbolt display and my Macbook's retina display, I try to shut down my Parallels VM first, and restart it once the monitor change has been made. In the case of the big mouse pointer, I failed to follow said protocol.
Parallels folks, here is more info:
As far as I can tell, this issue is due to switching monitors, which in my case, involves either using my Macbook's integrated retina display, or my Apple Thunderbolt display. So, the following scenario lead to the giant mouse pointer:
* Running Windows 10 in non-coherence mode on the retina display.
* Sleep machine.
* Attach Thunderbolt monitor, and wake machine.
* Try to put the Mac to sleep (with Parallels VM still running). Sleep failed. Windows or Parallels crashed, and I needed to do a force quit, which took a long time to complete.
* Restarted, launched Parallels, and mouse pointer was huge. Restarted the machine multiple times, but this did not fix the issue.
In looking at Windows display settings, it appeared that the Win 10 VM believed that it was running on a monitor with the resolution of my retina laptop's display. Various attempts at restarting with the Thunderbolt display attached, detached, etc, had no effect.
Last edited: Aug 18, 2017