Niel, maybe its going out too hard all at once, doing hard, long mileage right out of the gate can be just more than your body wants to take on. A few shorter rides to gather up some endurance and seat time can let you become more enthusiastic about riding. I'd agree with some rides to just cruise about, stop some and look around your area to see what you are flying past while out on a training ride, going hard. Throwing in a few screw around rides each week helps me keep from burning out on riding.

This too shall pass, don't get discouraged about things early in the season.

Bill