htaccess getting overwritten over and over = 404 error

I have been having a big issue on my wordpress blog and don’t know what to do right now. To make it short, my .htaccess file is getting overwritten over and over…

These lines :

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

are duplicated a hundred or thousand times with NUL characters, and my .htaccess is now 1.5 Mo ! I can fix the issue by uploading a clean .htaccess, but the issue occurs a few hours/days later, again and again, and the pages of my websites just show a 404 error…

I also tried to put the htaccess file attributes to 404 instead of 604 to stop it from being rewritten, but my host doesn’t allow this and it came back to 604…

WordPress : 3.6.1
Plugins : Akismet, Anti-spam, DB Cache Reloaded Fix, Do Follow, Google Analytics for WordPress, Post Ratings, Recipe Card, Tweet, Like, Google +1 and Share, UberMenu, WordPress Database Backup, WordPress SEO, WP Sitemap Page, WP Super Cache

Any clue ?

Best regards 🙂

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