After installing K2 and when I am trying to register to the site i am getting this error

"Fatal error: Call to a member function def() on a non-object in /home/www/boscosevakendra.org/components/com_k2/templates/register.php on line 31"

The joomla registration process was not getting thru. What could be the problem? How to overcome this problem?

Thanks in advance

shansand