The game wouldn't let me return after being alt-tabbed, so I closed the application and restarted it. I've done this a few times with no problems. This time, every single map in the game has a graphical glitch. The glitch goes away if I hover over an interactive portion of the map, like a character name or a waypoint. Here are a few screenshots of what this glitch looks like:
http://i.imgur.com/aDJq4Bu.jpg
http://i.imgur.com/UG0Yi11.jpg
I went through steam's "Verify game files", and it finished saying it was successful.