You should be posting your data (via <form action="" ...>
to your theme options page, rather than to the wp-admin/options.php file. The latter is for the stuff under Settings.
Also, I don’t mean to be tossing dirt at anyone in particular, but always take the tips that you read on the web with a grain of salt. This post on the same site, as an example, offers extremely bad advice:
http://themeshaper.com/customize-blog-posts-touching-theme-files/
function myblog_shareontwitter($content) {
print $content; ?>
<p><a href="http://twitter.com/home?status=Currently reading <?php the_permalink(); ?>" title="Click to send this page to Twitter!" target="_blank">Share <em><?php the_title() ?></em> on Twitter</a></p>
<?php }
add_filter('the_content', 'myblog_shareontwitter');
The above code is completely broken: “the_content” is a filter, WP expects $content to be returned rather than echoed, and WP (not to mention plugins) expect $content to still be around after that function gets called. Moreover, the_title() will return garbage if you’re not in the loop; this is problematic in that automatically generating an excerpt outside of the loop will call “the_content”.