Unable to edit workflow task from word document

Hi All,

Currently, we've configured an OOB Approval workflow on one of our SharePoint library.
We are facing issue of not being able to edit the workflow task from the Office documents.
As workflow initiator, the task gets assigned to an approver. The approver can then edit the task from the document
on which the workflow has started and reassign to a new approver.
But the new approver now cannot open the task from the word document on which the workflow has started.
He can view\edit  the task directly from the browser or from outlook mail but not from the word document.

Environment
SP2013, Office 2007
Doc Types: *.doc *.docx

Any help is much appreciated.

Thanks
Vijaya