Strange. I would suggest opening a support ticket. Be sure to include diagnostics.
There could be a similar behavior caused by different time(s) on some of the computers running following instances: Netflow Traffic Analyzer service, Web concole, Database server. If this is your case then I would recommend adjusting times so that they are same on all computers running mentioned instances (as NetFlow Traffic Analyzer currently does not support multiple time-zones solution). Otherwise you may need to open a support ticket.