Hello Les;
What are you doing to cycle your tank with no fish? Are you dosing it with ammonia? What are your other readings (for ammonia and nitrites)? It seems that your process has stalled. Providing you've been dosing with ammonia during the process, it seems you've grown enough bacteria to handle the ammonia and the nitrItes those bacteria create but somehow the bacteria that change nitrAtes to nitrogen aren't growing. It may mean that you just need to be patient. I wouldn't recommend water changes during a fishless cycle. The high nitrAtes aren't hurting anyone right now and you'll keep a good supply of food in the form of nitrAtes to grow the right type of bacteria.