This extension has integrated anti-spam protection, which uses Joomla core tokens to prevent spamming. More than 40.000 sites are already using this contact form, and nobody had such problem.
Probably your server has some issues with session variables, that is why integrated anti-spam did not work for you correctly.
If you had written in our support forum, we would solve the issue for you quickly. Please in such cases write in our Support Forum, or send as email, instead of writing such a bad review.