OK, so every time I try to use a link from the My Games library page, I get a 403 Forbidden error. I tried downloading the GOG downloader, but it doesn't show anything to download. I'm using a Mac on Mountain lion and have tried Chrom and FF and get the same error.

Any ideas?

Cheers,
Andrew

The 403 is usually the result of a proxy. The url you get from the "My Account" page has a session id that is IP specific. If for some reason the IP you visit GOG is different from the IP the CDN sees, you get a 403. Go to "My Account", click on the game you want to download, set "GOG.com Downloader mode" to on and click on Mac OS X installer. The downloader should pick the link and start downloading.