Why does this produce a "Request exceeded the limit of 10 internal redirects"?

Question

I can't find why I'm getting the following error:

AH00124: Request exceeded the limit of 10 internal redirects due to probable configuration error. Use 'LimitInternalRecursion' to increase the limit if necessary. Use 'LogLevel debug' to get a backtrace., referer: < URL >

Could it come from the multiple conditions in .htaccess?

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]+)/([^/]+)$ /index.php?id=$2&user=$1 [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]+)$ /index.php?id=$1 [L]

Order Allow,Deny
Allow from all
Deny from 198.51.100.0 # spammer

<Files "secretdb">
Order Allow,Deny
Deny from all
</Files>

PS: I already read Request exceeded the limit of 10 internal redirects but I don't see the solution.