The manage task dialog does not use BrowseBean for it's context, the call you have made is used by dialogs that act upon nodes held in spaces.
The manage task dialog is dealing with a node within a workflow (not a space). The workflow however, does have a list of resources which point to documents held in spaces. You can access these nodes but it needs a different approach.
I need some more information on what you are trying to do to help you further. What is the link supposed to do?
