.htaccess Help

I hope somebody can help me with an issue I’m having with .htaccess.

I installed some plugins to create an intranet area on my client’s website: Add Multiple Users, Page Security by Contexture, TinyMCE Advanced.

It seems every now and then that the contents of my .htaccess triggers an internal server error. When the first one happened it turned out that the .htaccess had disappeared completely. This weekend the server workers replaced the .htaccess file with another to correct it. I’ve posted the contents of the original .htaccess below – the engineers have suggested I review the rewrite rules to correct the problem, but this is beyond me!

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

## END WordPress

Thank you in advance for reading this.