The following is 100% anecdotal from a very, very late night (or a earlyish
morning immediately following a late night...) and the last bug to be fixed
before delivery to the client & bed...

In your Sorting & Grouping window, review the "Keep Together" property for
your groups (main report and any subreports). If any of them are set to
"Whole Group", try changing them to No or "with First Detail" and see if
your report runs.

I vaguely remember that having this property set to "Whole Group" in a
particular case caused a similar problem for me once and by changing the
setting I got it working. It was as if there was too much data to fit on one
page so the "Whole Group" setting prevented Access from formatting the page.
Normally, this kind of "conflict" shouldn't cause this behaviour (per Help,
if it can't follow the instructions, Access is supposed to ignore them), but
it certainly seemed that it was causing Access to choke on *some* datasets,
but not others. There may have been something else going on (i.e., this
setting in conjunction with some other combination of
visibilty/shrink/grow/NewPage settings and the report did include a
subreport), but once I got it working again, I didn't pursue it. So maybe I
just came across 'a' solution, not 'the' solution.

Good Luck & HTH,

Check your memo field contents for week 18.  I suspect that at least one of
them exceeds the amount that will fit on one page.   If you have Keep
together set, Access seems to hang when it is formatting the report.  It
appears to keep looking for a page where it can keep all the information
together.