Fabio, just checked and this line exist in prepare.php, x-cart 4.2.3.
If you use older version in 4.2 branch, replace:
Code:
if ($k != "GreetingCookie")
with:
Code:
if ($k != "GreetingCookie" && $k != "fbs_xfacebookconnect" )
Please contact me using contact form on 7dana.com if you have any problems with installation.