Thank you for contacting us.
First of all, are you sure you are using our plugin? Because the latest version is v1.3, not 1.6.15 🙂
404 error is a common error in WP, if you have the latest (which is v1.3) installed, it will automatically flush the rewrite rules upon activation, if not, you can always go to your settings -> permalinks, click on save without changing your settings.
If you are indeed using our plugin, please provide information of how to trigger your error.
We can’t help you unless you help us 🙂
