WordPress doesn’t know that you want the path /searchmyblog/
as search result base. So when it sees the a
it tries to find the best match – in your case a post starting with this letter.
To fix that you could modify my code for the pagination base to change the search base:
if ( ! function_exists( 't5_search_base' ) )
{
register_activation_hook( __FILE__ , 't5_flush_rewrite_on_init' );
register_deactivation_hook( __FILE__ , 't5_flush_rewrite_on_init' );
add_action( 'init', 't5_search_base' );
function t5_search_base()
{
$GLOBALS['wp_rewrite']->search_base="searchmyblog";
}
function t5_flush_rewrite_on_init()
{
add_action( 'init', 'flush_rewrite_rules', 11 );
}
}
Now your .htaccess
should work.