Yeah, I just experienced this issue myself... any suggestion to fix it? Just don't altab?
I had this happen to me only once 2 days ago.
Most probably that was due to an overheating vga card. Unfortunately, it happened in the most annoying and embarassing time, ingame and while fully deployed. Loosing my units isn't so much of a problem, but having to exit a 4v4 gamr and leaving your team crippled is.