[Crash] Mac client ARAM crash upon buying

I'm not sure if this is specific to macs or not but I'll describe:

I will join and load an ARAM. This hasn't happened on any other map for me. I'll open the store by pressing "p" and I will either be able to buy a couple items or immediately the game will freeze. I have to do a hard restart. It has happened when I have Gnar, Janna or Lux though I don't think it's champ specific.

I'm running a mid-2010 i3 macbook pro with Yosemite - all software has been updated and nothing truly out of the ordinary appears that I can tell. No other applications are running in the background