Your computer is way under the minimum specs to run TS3. Both the processor and the graphics card don't come close to requirements. Whether this mac could handle the base game on the lowest graphics settings, I don't know, but even if it could, the stress of the game might take years of the life of your laptop.
As far as the unknown error itself, it could be due to having certain packs installed, to the game not detecting your graphics card, or just due to your macbook being underpowered. If you really want to try to play TS3 on this computer, the first two problems can be addressed, but the third might still be an insurmountable barrier. I'm sorry I don't have better news.