Hello,
1) Please check the rights for folders. Here is a documentation regarding this question:
http://codex.wordpress.org/Changing_File_Permissions#Shared_Hosting_with_suexec
Also try to deactivate other plugins and check if the problem stays the same.
2) Please provide an access to admin area, so that we could find the problem. Here is our support http://support.bestwebsoft.com/
Did you have some problems when you do the update? Did you update only Wordpress or also something else?
Kind regards,
Support Team