So if you alter your RT to test fot counting only reviewdates what value do we get...
name = whatever
field to summarize=ClearQuest.id
summary type = distinctcount
evaluate = use a formula
{ClearQuest.review_date} in last7days
reset=never
place in the report footer
If 0 (or empty) look on your detial rows where you know that one of those dates exists and look to make sure there is a value that is a non NULL for the ClearQuest.id on that same detial row.
What does this test give us?