The Slide Show Accessory runs as a separate program from PC Access. However, the Slide Show Accessory understands the PC Access configuration files. When you run the Slide Show Accessory from PC Access, PC Access tells the Slide Show Accessory the Agent ID for the current agent. This error message indicates that something is wrong with the Agent ID the Slide Show Accessory received.
Write down the Agent ID the error message reports to you. You can compare this to your current agent's ID on the PC Access Add/Edit Agent window. Follow the instructions for an Internal Error.