This error occurs when the Sharing and Permissions levels aren't properly set for the .dat file of the plugin. 

Locate the .dat file on the computer. Hold Command (Apple Key) and press 'I' to "Get Info" on the file. Under Sharing & Permissions (Ownership and Permissions), make sure that everything is given Read and Write access. 

Additionally, assign your username to the 'Name' pull-down menu, if it's not there already.