I also had the same problem...after going through all the posts in this community i came to know that the support from Mibew team is poor...
But i found out the solution to this problem...
In the php.ini file search for the "session.save_path" . It will look something like this : session.save_path = "/var/lib/php/session". (The path will be different based on your installation.)
Go to that location. Give the full root permissions to this "session" folder.
Restart apache...
Now your mibew visitors page will be shown properly...(CrossChecking :: Now you can see files getting created under the /var/lib/php/session directory when you login to the visitors page in Mibew)...