Frozen Black Screen

I'm going upload this again writing, because this problem really bugs me. I believe such a problem might've affected others already, and I think that there's no simple way to know how to fix it, or what the cause is without some help.

** [CRASH] I get an "infinite" black screen after champ select**

So erm, for the past three days or so, I've been receiving a black screen on my league client. It happens in between the Champion Select screen, and the loading screen (into the game) as it opens. I've had no issues when I login, open the client, and such too.I use a MacBookPro, and its on OSX ver. 10.8.5 (I'm not able to update my OSX on this computer. My dad already warned me that my MacBookPro won't be able to handle the new version because it's so old.) I don't know if this has anything to do with it, but because of this issue I was placed into low priority queue just now. It could just be my new wi-fi box, considering it's quite unreliable, or potentially the recent intense weather. I don't know what's the problem, but I was wondering if anyone has any advice/help to this issue. Thanks~

The other day, I tried a custom game, Me (Leblanc) vs a Beginner Tristana bot. Same thing happened, Champ select's over, IMMEDIATELY turns into a black screen (also the cursor can move, but it doesn't change into the glove looking one) then I force quit. This time however, the champ select is still going. The problem still isn't fixed and I don't know the cause of it.

-First, Everything from the launch client and the store etc. is perfectly normal. -Immediately after, once I join into a game I get into champ select, nothing wrong there. -Once champ select is over, the loading screen is black, and the cursor doesn't change. If I click anything or try to type while in this screen, it makes that annoying "DING" sound you hear from apple computers. -I force quit, and as usual it says "Reconnect" in the client. -I reconnect, and then the black screen reappears. -The second or third time this happened, I waited 20 minutes or so, and soon the game was over. But the screen didn't change, and so I closed League, then relogged into my account and the game had ended already. -Force quit, and I got the priority queue thing for not participating/afk

I've tried this maybe about 3 times already, and I have no clue as to what I can do or anything of the sort.