This is what I used to get clean urls working on 1and1 hosting
In .htaccess replace the former with the latter:
- RewriteRule ^(.*)$ index.php?q=$1 [L,QSA] + RewriteRule ^(.*)$ /index.php?q=$1 [L,QSA]
+ RewriteRule ^(.*)$ /index.php?q=$1 [L,QSA]