Why Is Serving Ads So Difficult?

Chip asks: "Many moons ago ('85) I started a sports publication and we have been moderately successful. We finally put the entire site on the Web in '95 & have learned a little as we went along. It was much more expensive than we ever imagined & frankly we lost money keeping the site up & maintained every month. One of my subscribers introduced us to banner advertising (Flycast, DC, Burst) about nine months ago and we thought it was a God-send...at first. Now I have people complaining all the time since my site doesn't load as fast, sometimes kicks people off, and so on. I don't know what to do or who to call, every ad agency and ISP we use blames someone else. Can someone refer me to an ad agency (or software that I can use to do it myself) that delivers ads that don't slow my site down or ruin the experience for my readers? I desperately need the revenue generated but can't stand the 24/7 headaches. I know this may seem juvenile to all you "experts" but I have no clue how to fix it and don't want to go back to losing money on my site. Suggestions?"