404 rrror across WP site

[ Moderator note: title adjusted, please refrain from using help, urgent, emergency, asap, etc. in topic titles. ]

I’m suddenly getting a 404 error on my WordPress installation – 192.185.12.94/~admin5k/

I’ve gone in and changed the .htaccess file to .htaccess-backup, I’ve gone in and looked at the file contents and even changed it to the recommendations I’ve found:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /~admin5k/
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /~admin5k/index.php [L]
</IfModule>

# END WordPress

Any suggestions?