"Next/Previous posts" does not work. Help!

Ok, I have found out that a line in index.php that makes the frontpage only show a certain category, is creating the problem:
<?php query_posts(‘cat=18&showposts=’.get_option(‘posts_per_page’)); ?>

I don′t know how to solve it though. Anyone?

try:

<?php query_posts('cat=18&showposts='.get_option('posts_per_page').'paged='.get_query_var('paged')); ?>

https://codex.www.ads-software.com/Function_Reference/WP_Query#Pagination_Parameters

Thanks!
Unfortunately that did not change anthing ??
Other ideas?

If it helps to see what is going on, here is my index.php:
(If I remove the line in bold, the problem disappears, but so does my selection of category.)

[code moderated – please use the pastebin]

my bad – forgot the ampersand & before the 'paged=';

<?php query_posts('cat=18&showposts='.get_option('posts_per_page').'&paged='.get_query_var('paged')); ?>

hopefully, this gets it to work …

Yihah! You did it!
Thanks a bunch!