When I log into GW2 and start playing, within about 5-10 minutes it shells (alt-tab) to win. Funny thing, it takes two alt-tabs to get back into GW2 (suggesting it's still in GW2?!?). It never happens again during that game session.
I turned off win notifications completely, but that made no difference. Any ideas? I've had this same exact setup for 3 years now (computer/router/fiber), and this NEVER happened until just recently.