Mod_rewrite forces 404 ?

Hi, My ISP & I are trying to troubleshoot why my blog (https://www.linickx.com/blog) died; I know it’s not a theme or plugin thing as the admin page (https://www.linickx.com/blog/wp-admin) doesn’t work. (It’s wp version 1.5.1.3)

Now I’ve had the following e-mail from my ISP

<quote>
I have been looking into your script problems today, i have spent a lot
of time looking at it. First i thought it was a problem with MYSQL, i
then ruled that out, and managed to find a certain line of code in the
wp-blog-header.php that worries me. It seems that the header file forces
a 404 error until a certain criteria is met, and the criteria is
something to do with rewrite rules:

// If we match a rewrite rule, this will be cleared.
$error = '404';

// Fetch the rewrite rules.
$rewrite = $wp_rewrite->wp_rewrite_rules();

If you ask me, i don’t think it’s the best way to code a script, it
would be more useful to display an error message, rather than force a
404 error. If you could contact wordpress, and ask them what re_write
rules need to be enabled, i will be happy to review them, and install
them if necessary.

I am sorry for all the trouble you have had with this, but we are as
desperate to solve it as you.

Let me know if you need anything else
</quote>

I’ve had a search, & codex says mod_rewrite is optional, so I’m confused.

Can the ISP config of mod_rewrite cause the wp .htaccess file to break & force a 404 ?

Thanks in advance.