error in workflow

HI Gurus,

I am executing a workflow with the following steps,

First step is a condition step on company code

Second step is a approval step by sending mail to the HR respective group based on condition company code.

For sending mail I used object type Selfitem and method sendtaskdicription.

Now i am thrown with an error stating the sendtaskdescription method cant be executed. Can any one say why and how to rectify the problem.

I wrote the content of the mail in the discription. I didnt pass any values to the method container.