Forced alt+tab at the start of game (right after champ select)

So I played my first game since July of 2015 today and, unsurprisingly, met anannoying bug. After champ select was over my game client launched. It was non-responsive for about 30-45 seconds. Then it started responding. During this entire process i was forcibly alt tabbed out of the load screen. I knew the game was running fine because I could hear pings, heard the announcer's messages, all that good stuff. So after 3-4 minutes of frantically searching for a fix, I tried alt tabbing in again and it just worked. While I was still able to play my game and not let my team down I'm kind of disappointed that bugs like these still happen. Is this a dual-monitor thing? Should I run in borderless windowed?