This happens to me daily, I have no way to tell if it will happen, sometimes i get into dynamic queue and i cant see a lot of the tabs to click on and i know if i click on masteries or sometimes even if i don't, the client will crash and i am out 3-10 lp for no reason of my own and suspended from joining games for 6-30 minutes, i am one of the few who never queue dodge on purpose. To date I have lost over 100 LP just because of this bug.
Riot please look into this, it is one of the most frustrating things when trying to climb, I am currently in Gold 4 and would most likely be in gold 3 or 2 if it weren't for this.