Site Fatal Error

I just upgraded from v2.0.1.1 to the latest v2.3.0.2 and now my site is showing a blank page with this error:
Fatal error: Call to a member function start() on a non-object in /home/smssenda/public_html/shop/catalog/controller/startup/session.php on line 16

Any help resolving this will be highly appreciated.

How did you perform the upgrade? Do you have a backup of your site?

Also: viewtopic.php?f=181&t=145937

Many people have problem with site fatal error.
What you were doing at the time of the error?
Do you have MODS installed?
What is the code on line 16?
Importing from host to local host???
You can consider some topics:
viewtopic.php?t=160329
http://stackoverflow.com/questions/1424 ... non-object
viewtopic.php?f=20&t=24313