Ustable session? works on local server

Hi.

I know You guys will help me out. Right?

Attached file is a zipped version of this pseudo shopping site. All it´s supposed to do is send an e-mail with all the products user chose. The first file is boutique.php. Please oh please have a look at it. I´m a complete noob to php. This was build with help from a friend of mine. but he´s clueless as to why it wont work. I get this error when on a remote server:

Fatal error: Call to a member function on a non-object in /home/httpd/vhosts/softlares.com/httpdocs/boutique/add.php on line 15

on my local apache it works fine.

Also, i debugged it with phpEd and it shows my cesta object in $_SESSION well constructed, but empty. Then it does what it should on local. Anyways, i´m about to stomp the screen and eat the keyboard so … i´ll just hope someone takes a look at it and them what the heck.