Even in the INI.AppendString-Function the output is wrong. It will append the item, not the string! The value output of the Write-Value-Function is correctly outputed.
This looks like a bug in the Plugin for the INI-Control. Maybe the wrong variable is set for the string-output.
I would lookup and fix it in the Source-Code itself and upload patch for it, but the plugin-code in the CVS are binary!