Sims 3 Launcher crashes when logging in (Mac)

I am currently unable to login to my Sims 3 Launcher, in order to download/install content from the Sims 3 store. After entering my password, and clicking Log In, the launcher closes. Every time! I have managed to bypass the launcher in order to play the game, but I want to install my new purchases and can't do that within the game.

I'm on Mac OS X 10.9.5, with plenty of memory space left and the most recent updates from the App Store all installed. 

It seems ridiculous that after spending money in the store, the programme then chooses to mess up, and you can't install or download purchased items directly while in the game. 

Does anyone have any good suggestions - I have already tried all the options in the forums about deleting particular files and I've already set it up to bypass the launcher. I now open the launcher from within the game, but when I log in it still crashes.