My League Of Legends Loading Screen Keeps Disapearing

Whenever I go into league loading screen, it vanishes! and after that my league will not open, as it says it is already opened when it's not! So I always have to restart my computer due to this problem, and then causes my team to lose with 4 people. It has also caused several 20 minute bans to my account. So I would like to know is there anyway I can fix this problem?