Error while trying to install the base game: "Error reading game files"

At first all I wanted to do was install a few EPs, I bought the base game way before I knew about torrents and downloading and what not. Which didn't work well; as I had the bought-version of EP Pets installed, it kept saying I couldn't install other ones (not compatible with Pets, apparently). Though it did work for Ambitions.

^ If anyone can help me with that problem there, it would be greatly appreciated!! Sorry if it doesn't sound very clear to you, will explain further if you can help.

So now, I downloaded the base game from here (not the complete collection). The install goes well, until the "actual install", it gets an error saying "Error reading game files: $INSTALLVOLUME/Caches/". What do I do with this? Do I have to do something simple, like restarting my computer? Or do I have to do some crazy difficult things in order to have it working? (Also, please don't come at me saying I should've read the "*MUST READ* How to install The Sims 3 correctly." page properly, I'm literally stuck at section 1 so I didn't really have a chance to mess up with the other sections.)

Any help would be extremely welcome, I don't wanna buy all the EPs again...

(Mac OS X Mavericks)