Plugin options not showing up in the Options section

Hi, I’m the author of the wp-postalicious plugin ( https://neop.gbtopia.com/?p=108 ) and I’ve been receiving some emails about people who had trouble accessing the plugin’s options page inside the Options tab. The PHP error which is causing this behavior is:

Fatal error : Cannot redeclare neop_del_options() (previously declared in […] /wp-content/plugins/wp-postalicious.php:12) in […] /wp-content/plugins/wp- postalicious.php on line 11

which indicates that the plugin file is trying to be loaded twice by WordPress. (Note: I removed the full path and replaced it with […] but both paths are exactly the same) My first thought was that this was caused by a faulty upgrade where the user forgot to deactivate all the plugins before performing the update, but after talking to the user, he told me that he was using a fresh WordPress 2.1.3 installation. I also suggested deactivating all plugins and then only activating wp-postalicious, but that didn’t work either.

Does anyone know what the cause of the problem is and how to fix it?

Thanks in advance