If you try to load a plug-in from a shared network server that wasn't added to the GAC (Global Assembly Cache), it will fail to load.
You need to give your plug-in a strong name key and move it into the GAC:
Create a strong name key for your plug-in.
From a command-prompt, type the following to add the assembly to the GAC:
gacutil /i \servername\<plugin_path>\YourPluginName.dll