The problem here is that the Blix theme is rather old. On its homepage, it states:
‘Blix’ is a freely available theme for WordPress 1.5.
I just installed it locally and am experiencing the exact same problem you are. This is due to the fact that the themes uses a custom query to get page links in header.php
Around line 35, you will see this block of code:
$pages = BX_get_pages();
if ($pages) {
foreach ($pages as $page) {
$page_id = $page->ID;
$page_title = $page->post_title;
$page_name = $page->post_name;
if ($page_name == "archives") {
(is_page($page_id) || is_archive() || is_search() || is_single())?$selected = ' class="selected"':$selected='';
echo "<li".$selected."><a href=\"".get_page_link($page_id)."\">Archives</a></li>\n";
}
elseif($page_name == "about") {
(is_page($page_id))?$selected = ' class="selected"':$selected='';
echo "<li".$selected."><a href=\"".get_page_link($page_id)."\">About</a></li>\n";
}
elseif ($page_name == "contact") {
(is_page($page_id))?$selected = ' class="selected"':$selected='';
echo "<li".$selected."><a href=\"".get_page_link($page_id)."\">Contact</a></li>\n";
}
elseif ($page_name == "about_short") {/*ignore*/}
else {
(is_page($page_id))?$selected = ' class="selected"':$selected='';
echo "<li".$selected."><a href=\"".get_page_link($page_id)."\">$page_title</a></li>\n";
}
}
}
Delete it and replace with:
wp_list_pages('title_li=&depth=1');
This worked for me but I would strongly suggest going with another theme that is more up to date.