Browsers won't access links from google

Occasionally when I search for something on google and click a link my browser will start loading and then time out after a minute or so. However when I try and access the webpage a different way it works fine.

Example:

I google "Velveteen Rabbit"

The first link is the wikipedia article.

Clicking on it starts loading and then freezes until it times out.

However I can go on wikipedia.org and type "Velveteen Rabbit" in the search box and it takes me straight to the web page no problem.

Most links will work. I've mainly had the problem with wikipedia and stackoverflow.

The same problem occurs in Safari and Chrome. I'm using the latest versions on Yosemite with a 13-inch Macbook Pro bought in 2011.

There's no issue on a windows computer using the same wifi.

Any help would be fantastic. I'm flummoxed.