problem come from htaccess
try this one:
RewriteEngine On
RewriteCond %{REQUEST_URI} ^(.+)\~s$
RewriteRule ^(.*) /stats.php?u=$1 [L]
RewriteCond %{REQUEST_URI} ^(.+)\~d$
RewriteRule ^(.*) /delete_file.php?u=$1 [QSA,L]
RewriteCond %{REQUEST_URI} ^(.+)\~i$
RewriteRule ^(.*) /share_file.php?u=$1...