This is the classic symptom of an oversubscribed ad server.
The server has more requests for ads coming in than it can handle. It backs up, forcing webpage readers to wait, and often causing the ad or the page to return a 404 not found error.
Thank-you for your reply ;) ; interesting. I learn something new everyday on Daniweb. :)
**EDIT to his post: when posting this it took over 1-minute. It is habitual now.