I had a ridiculous crashing to desktop (with no error message) problem, basically couldn't play the game. Any time I was in combat it was a matter of time before I would crash to desktop.
I went through tech support and worked through everything they asked me to do to resolve it to no avail.
With a combination of intuition and checking the Windows error reporting system and researching every fault bucket item I finally found X64 headed errors that were linked to the mouse.
Switched mice, crashing has ceased.
I don't have a why or a how, but I'm just putting it here because it was likely I would have had to do very drastic things on the whim of tech support to fix something they would have never found. Nothing against tech support, I guess they might have made it to the mouse being the issue eventually... but fyi the G502 worked fine in everything else, it was just crashing eso for me.