problems in Bussiness inbox

Dears :

in my workflow there is a user decision, and in the decesion i have some decision options such as a activity wich is a task to display something with Work item text DISPLAY_ST

Sometimes, when the agent receive workitem in inbox, then execute the user decision and choose the activity. It will call the task and display something.

At the same time when i refresh the inbox, i will receive another mail entitle 'DISPLAY_ST' . (the name of Work item text ).

it occurs sometimes. any advice?

BTW, the agent for user decision is two user id. And the agent for the task is general task.