edit: well done - you sorted it while i am busy typing here ;-)
just downloaded the theme -
the custom field key for the thumbs on the two section on the home page is 'thumbnail'
while the bottom section looks for the custom field key 'hpbottom'
if you want to use the same thumbs as in the top sections, change the code in these lines in home.php:
<?php if( get_post_meta($post->ID, "hpbottom", true) ): ?>
<a href="<?php the_permalink() ?>" rel="bookmark"><img style="float:left;margin:0px 10px 0px 0px;" src="<?php echo get_post_meta($post->ID, "hpbottom", true); ?>" alt="<?php the_title(); ?>" /></a>
to something like this:
<?php if( get_post_meta($post->ID, "thumbnail", true) ): ?>
<a href="<?php the_permalink() ?>" rel="bookmark"><img style="float:left;margin:0px 10px 0px 0px;" src="<?php echo get_post_meta($post->ID, "thumbnail", true); ?>" alt="<?php the_title(); ?>" /></a>
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re: archive page:
can you repost the code (please use the pastebin) ?
where does this code section come from?
the problem is - i can't see any default thumbnail images at the bottom of the category archive page.
can you post a link direct to a category archive page which is showing a default thumbnail image?
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edit 2:
if this is all working now, please mark this thread as resolved.