Strange Lighting Bug

[WrongEnd]

Note, this is running on a Windows machine.

I tried to play on the extended server and I got this. I don't know how to replicate it, but what happened was that I set my status to ready on the lobby screen, after we had finished a five hour round. I alt tabbed and browsed the web, and when I tabbed back in I got that screen. I could still interact with items and right clicking to see what was on a tile worked fine. I could also see the chat at use it perfectly fine. Re-logging seemed to fix it.