go to include----> config.php
find and replace cookie setup with this lines
Code:
// Cookie setup
$TBDEV['cookie_prefix'] = 'tbalpha_'; // This allows you to have multiple trackers, eg for demos, testing etc.
$TBDEV['cookie_path'] = ''; // ATTENTION: You should never need this unless the above applies eg: /tbdev
$TBDEV['cookie_domain'] = ''; // set to eg: .somedomain.com or is subdomain set to: .sub.somedomain.com
and retry to login
hope this helps