As Sledhead said, welcome to the world of event photography!!
My initial thoughts are that your ordering method is not obvious, buying an event photo is an impulse thing. I had to look at your page as what to if I wanted a print, whereas most event photographers use a shopping cart of one kind or another so that as soon as someone looks at an image they also have a range of purchasing options in front of them as well.
I know many users of this forum rave about Flickr, but they are not usually people wanting to sell prints. Also note, that your thumbnails are cropped to squares which is slicing heads. A lot of people will think that you have shot the image like this and look no further. You have to think how the punter thinks, not how you as a photographer thinks, when it come to web selling. Get yourself a dedicated website - the sale of 6 7x5 prints covers the costs of mine for a year, they are not expensive.
I also shoot a lot of running events, and your images could be improved. Full length, arms and legs pumping, out sells everything else put together. If you can get an out of focus runner in the background, so much the better. Close ups, and shots from behind rarely sell although side on occasionally do.
Ditto for the cyclists.
Equestrian photos that sell well tend to be of the horse on the way up over the jump with the horses ears up, front legs bent under and the riders head the same side of the horse as your camera.
I've never shot any shooting event, but it looks like you were told where to stand?? Probably for H&S reasons I guess.
I hope I havent come accross as harsh, but this is my thoughts upon looking at what you are showing.