If an user adds a new field to the "Communication To Do List" the icon for "Has Attachment" does not display anymore. A "Y" is shown instead.
Resolution / Workaround:
If you carry out the following queries the problem should be solved:
select * from custom_lists where GriP_GridName like '%todo%' and GriP_ColName like '%hasatt%'
update Custom_Lists set GriP_ViewMode = 'ATTACHMENT' where GriP_GridPropsId = '[Id_from_previous_Query]'
This is an issue in version 7.1, but has already been resolved in version 7.2.