Happened a few times, not sure how to reproduce.
Windows 10, dual monitor setup, Nvidia graphics card.
GalCiv III in one window, Firefox in the second.
Firefox is running Pandora (Flash) or Netflix (Silverlight)
Play for awhile, can pause Netflix or let it run (I was watching Friends re runs).
Observed: Silverlight crashing, Pandora hanging / skipping tracks, system reboot, graphics insanity leading to hard shutdown
Have not observed this happen when the browser is running youtube videos, reading forums, or checking email.
Have not tested with Chrome yet. Does not happen with Skype, Amazon music, or Kindle.
Seems graphics related, sometimes the game will hang for a second when a star system is revealed, that is often when this will occur.
I play on Gigantic maps.