Game Crashing

I came back to LOL after a few months away, and I noticed something.. Every time I play in botlane (Whether I'm a Support or an ADC) the game ALWAYS crashes at around 5 to 10 minutes.. Alt + F4 does not work during this period and I can't hear anything or do anything on the PC.. I have to turn the computer off from the button and restart the whole client.. People have been reporting me for AFK Behaviours and it's not my fault.