Your syntax is wrong, change:
query_posts( array(
'post_type' => array(
'post',
$include_reviews,
$include_screenshots,
$include_videos
),
'paged' => $paged )
);
to:
query_posts( array(
'tax_query' => array(
array(
'taxonomy' => 'category',
'field' => 'slug',
'terms' => array( $include_reviews,
$include_screenshots,
$include_videos )
)),
'paged' => $paged,
'post_type' => 'post')
);