Last few patches my firewall asked permission but the game didn't crash. This patch, it's the missing dll error again and the game had trouble starting even after I put the firewall into learning mode trying to get back into the game.
1. Forget to load up a custom bot game on the first game after patching
2. Join any map (I joined Summoner's Rift vs AI)
3. Game crashes after champ select and while loading the game with a message that msvcp80.dll is missing
4. Re-add firewall permissions for newly patched files
5. Wait and click the orange "Reconnect" button several times
This time was unique compared to previous patches in that even after I'd updated the game's permissions into my firewall the missing dll error came up twice more while trying to reconnect to the active game. I was level 1 vs level 7s by the time it worked.
However after the second time I had to log out and in again, the orange "reconnect" button remained on the client and I didn't have to log out again to keep trying.
I strongly suggest keeping the Reconnect button on the platform screen while any map is active. That way in case the loader crashes you can reconnect to the active game without having to log out and in again.