I've created some subsummary fields. When I create a report the first time it works and shows the summary information below the groups I want to sort. When I come back to this layout summary totals are gone.
What gives is that if you check the status area toolbar, you'll likely find that your records are unsorted. The found set must be sorted in a sort order that includes the "sorted by" field specified for your sub summary layout part. If you are not sure which field is so specified, double click that layout part label while in layout mode to open the appropriate part set up dialog.