It's ok, just found the solution:

in includes/modules/featured_products.php , change
$col_width = floor(100/SHOW_PRODUCT_INFO_COLUMNS_FEATURED_PRODUCTS);
for
$col_width = floor(100/SHOW_PRODUCT_INFO_COLUMNS_FEATURED_PRODUCTS) - 1;


The same patch should be made to
new_products.php
specials_index.php

thanks, Peter