Drag and Drop Issues

I have always used Tasks for payroll - created a task and when I get an e-mail request, I just drag the email over to the Task and drop it in the body so I always have back up of what was requested… all of a sudden when I try to drag it over, as soon as I get it hovered over the task, I get a red yield icon and it will not drop the email into the task ?? Any idea what is happening ? Thank you