Ran fine last winter. Won't turn over now. Replaced the ignition, battery, fuel and spark plug. Have confirmed am getting no spark out of the plug. What should I look at next?
In addition, the engine will not even try to turn over except maybe half the time. The other time I get nothing and it just makes a clicking noise. Are the problems related?

If the unit set over winter, chances are that mice may have built a nest under the blower housing (top of engine), and could have chewed wires in two. Check under the blower housing for damages.