It is important to avoid using both the PhoenixMiner hardware control options and third party programs (e.g. Afterburner) at the same time. While we use the AMD provided API to do most of the hardware control and monitoring, most of these programs use lower-level undocumented access and doing both at the same time can lead to driver lock ups. Note that Afterburner must be completely closed, not only minimized to tray in order to stop interacting with the GPUs. Or, alternatively, you should use only Afterburner (or other third party program) and none of PhoenixMiner hardware control options.