are you using net balancer? It runs a check to see if your IP has changed before it does an update, and actually I believe I manually changed that interval to make it higher. But it wont do an update unless it sees your IP has changed, and if you use net balancer you will need to make sure it can only access the 3 ips for the ‘checkip.dyndns.org’ site for the IP you want it to use. In the balancing rules you can set those 3 ips to only leave a certain interface. If ones down it will go out the other but unless your interface gos down every minute there shouldnt be a problem anymore.
I made big assumptions here that you might be using net balancer since I had this same blacklist problem, if your not I apologize for wasting your time. 🙂