My league is broken

I've played dozens of matches with no error, earlier I downloaded the 5.4 patch and now when I start a match I'm instantly brought to the game crash screen and when I try to reconnect it has only failed (like 300 times). So far 4 matches with my friend have been ruined, yes I have tried a repair... wtf am I suppost to do, literally nothing will work once match is setup yet everything before that is problem free, and closing/reopening client doesn't help.

Also if I click reconnect enough I get a message saying

the instruction at 0x01b54141 referenced memory at 0x020fe028. The memory could not be written

Click on OK to terminate the program.