If the content file you are trying to stream is too large (i.e. 400MB) you can get a couple of different errors including, "Invalid test configuration thrown by Wrservers: Not enough memory" or "Insufficient disk space".
In either case the suggested action is use a smaller content file. Unfortunately as memory is shared between these files and the test configuration there is no hard limit that can be set. Ultimate, you may need to try a few file sizes to find a file that will work with your given configuration.