Writing a plugin – throwing blank page when turned on

Hi,

I am trying to write my own plugin which lets the admin to change some options of the website. When I turn on the plugin it works fine – i can reach it through the menu and it does what I want it to do. However, when it is turned on I can not log out from wordpress – it throws the blank page. It keeps working (logged in) until the session expires. The same is when I try to log in (to reach the wp-admin page from another computer or when the session expires and logs out automatically) – blank page as well.

I tried to search for a blank page problem in this forum, also tried to google, but it usually states different issues and I could not find a solution to my problem. Can someone help?

The plug-in is just one file and it looks like this:

<?php

/*

Plugin Name: Nustatymai
Description: AGAISA puslapio nustatymai
Version: 1.0
Author: AGAISA

*/

add_action('admin_menu', 'load_plugin');
add_action( 'admin_init', 'register_mysettings' );

function register_mysettings() {
 register_setting( 'myoption-group', 'email_klausimui');
}

function load_plugin() {
 add_object_page("Nustatymai", "Nustatymai", 8, __FILE__, "plugin_function");
}

function plugin_function() {
 //...
}

function mysql_update_1() {
 //...
}

function mysql_update_2() {
 //...
}
?>

Thank you.