Using the Event View panel options you can tell the Event View engine to output the events to a .txt and/or .xml file. AQTime displays this message if an error occurs when AQTime outputs data to the specified file. The most typical reason for this is that the file is currently open by another program (or by another AQTime instance), so AQTime cannot output events to the file. Make sure the file is not used by other applications and then repeat profiling once again.