[shorelineoftahoe]

Wow, that was a really dumb mistake on my part. The trouble is with the quotes in step 2. They were single quotes before, and they need to be double quotes. I'm updating the post above and reposting what's changed below:

This:

# sort by manufacturer mod begins
case 'manufacturer':
$left_joins['manufacturers'] = array(
'on' => '$sql_tbl[manufacturers].manufacturerid = $sql_tbl[products].manufacturerid'
);
$sort_string = '$sql_tbl[manufacturers].manufacturer $direction';
break;
# sort by manufacturer mod ends

Should be:

# sort by manufacturer mod begins
case 'manufacturer':
$left_joins['manufacturers'] = array(
'on' => "$sql_tbl[manufacturers].manufacturerid = $sql_tbl[products].manufacturerid"
);
$sort_string = "$sql_tbl[manufacturers].manufacturer $direction";
break;
# sort by manufacturer mod ends