I can't say that I've seen that behaviour myself.
For the summaries which you've already built, on the General tab of each of your Summary definitions, verify that the "Insert total line" box is checked.
For new summaries, examine your design preferences. The defaults for all new summaries are read from your preferences file.
The first dialog box of the wizard is the Start, which shows you the name of your preference file. Click the Next button to move on to the General dialog. This is where you'll find the "Insert total line" option. Continue on and Finish the wizard.