Mac Client Freeze

I've been having a problem where occasionally after first loading into the game, the game freezes completely. I'm still able to move my cursor, but I cannot interact with the game client at all, I can't minimize the screen, I can't exit, so I have to completely restart my computer. Longest I've waited for this bug to stop is about 5 minutes before I just restart. The problem seems to be more likely to occur in ARAM games and generally seems to occur after I've purchased an item or two, clicking on an item in the left side of the screen and then purchasing in the right side where it's components show up may be the cause of it. This problem has happened often enough that I've been punished via LeaverBuster. Once I restart and reload into the game, the game works perfectly fine.

I'm currently running OS X Yosemite 10.10.1, but the problem has been happening for several months. I didn't bother posting since its just been annoying, but getting a LeaverBuster penalty is rather distressing since I'm not the type of person to AFK.

I'll help out in any way that I can, but the problem doesn't seem to happen consistently. The past two games I played in both froze (both ARAMs).

The first I was playing as Anivia (base skin), I purchased a Catalyst of the Protector after pulling it up by clicking on RoA in the Recommended Items section on the left (I'm not sure, I might've bought a health potion too) before the game immediately froze.

The second I was playing Cryocore Brand, I bought an amplifying tome and ruby crystal before my game crashed. I believe I clicked the Haunting Guise in the Recommended Items, bought the Ruby Crystal and Amplifying Tome, and I might've clicked on Liandry's torment to double check if I needed another Amplifying Tome to build it or not.

The problem has happened on a number of champions and skins, however, I'm not sure what's up, and I'd really like to get this problem sorted out.