This can occur if running a Flow Forensics report without a router or interface filter over a period of time of longer then a few minutes.
When running Flow Forensics reports, being they are based on raw data, they should be filtered to a specific router, interface, or other filter that will limit the amount of data returned.
If running without any filter, you should only run the report for a few minutes worth of time.
If your reports are stuck in this state, recycle the Netqos ReporterAnalyzer Report service on the Console server and the Netqos NQMysql on the Harvester servers.
If the Netqos NQMysql service doesn't restart on its own, kill the mysqld.exe process associated with the Netqos NQMysql service from Task Manager.