If you have a heart rate of 150 or the graph has flat lined, which is a poor signal error, it is possibly due to the existence of other peripheral devices that might be in other USB ports on your computer.
Please try systematically disconnecting other USB devices and running the emWave program. It may very well free up the Module to work properly.
Also, having the sensor plugged into an non-powered hub can cause this sort of effect. If your hub does not have a power source, plug the sensor directly into your computer, as opposed to a keyboard USB port.
Sometimes, having Bluetooth or other wireless devices in the immediate proximity can cause an interference with the emWave hardware. Please try moving them out of the vicinity of the emWave hardware.
If none of these are the case, please contact HeartMath Tech Support for assistance.