[Evolution] missing calendar

[Carpetnailz <carpetnailz researchintegration org>]

I upgraded last night (Fedora 19 w/ Evo 3.8.5). I imported by
calendar.ics and all seemed fine. Then this morning I went into
preferences, added Sun and Sat to my work week and told it to start
workweek on Sunday. At that point my calendar content disappeared. I
tried restarting Evo but that didn't help. I tried re-importing the
calendar, but that didn't help. What gives?

Well, I thought, start a new calendar. Maybe that will help. So I'm
going through the new calendar routine and get to the point of telling
it to use an existing calendar. Fine. I select the calendar.ics again.
But now I see a check-box: "Allow Evolution to update the file."

What does this do? There's nothing in the help files that explains this
item.

Thanks.