Check the scheduling settings on the Default Software Contents Download Job task on the engine. Ensure it is limited to run once per day.
Badly enough, according to the CIC.log, despite getting rejected for attempting to contact the content server too frequently, CIC may be looping every 5 minutes to reconnect with the Content Server. In order to be removed from the blacklist more quickly, you will need to kill the running java.exe process that is hosting CIC.
Open Task Manager and enable the Command Line column. Look for a java.exe process that contains wrapper.jar and CACIC.jar:
Kill this java.exe process, which will shutdown CIC. This will change the task on the engine to the ERROR state, which is fine. Be sure to wait at least 6 hours before retrying the content download task, to ensure enough time to be removed from the blacklist.