Hi everybody!
i am using joomla 1.5.23 with the templete jvwintro
when i try to add a menu then a message just like "Invalid Token" is shown
the same problem is shown in the JA-Methys-Joomlart-Template
what the problem is? and what is the remady?
please reeply me soon.

Your admin session expired, or your browser is not set to accept cookies from the site.

Just clear your browsers history and try to do. if again error display create a new superadministrator and login with the new username and password

Thanks a lot @ Kraai and also thanks to sainigks.
The problem is solved.