pick/ban crash with the alpha client

I have a problem with the alpha client, first i join a pick/ban phase. Everything is normal for a while, but i start (or try) writing in the chat and my keyboard just stop working (crash). I think it's a problem with my pc but 5 second after, lol completely freeze so i cant ban or pick a champ. after, client is still open in the taskbar but when i click on it, a little white rectangle appear. 30 sec after that, pc is completely not responsive. I try to restart it , but its just not working (freeze again). I need to restart it manually. I got this problem like 3 time in a month and after 2 a make a full repair of my LoL. I just got it a third time as im writing this. Is there any option for me ? because its got me 5 game with bigger queue time (you need to wait 5 min to really get into the queue) and lp loosing.

thank you for you advice !