So they are there, but not showing in the calendar  views? Could they be getting knocked off and are accessible when you select the “More…” link?

For the days when they should be there, the "More..." does not appear. There are not enough items on the day (because of this situation) to create the need for "more...".

And yes, they are there if you look at the item list, and they appear on the calendar  for other days/weeks BEFORE this period and AFTER this period, but not during. Ex: If I look on Monday, 6 Mar, I see a recurring Monday item started in February. That same item does NOT appear on 13, 20 or 27 Mar, then REAPPEARS on 3 Apr and dates forward.

Does that make sense? Well, not the behavior--that stumps me. But the explanation?

You are making sense to me. We had the same oddball thing happen to a calendar  and I am racking my brain trying to remember what it was. It was posted about in this group, I will do some searching and see if I can dig it up. But from what I can remember, Todd was able to duplicate it on his machine and there was no resolution.

Ok, read through this thread and see if anything helps: groups.yahoo.com/.../7632

Our issue involved different views showing different events (where it shouldn’t be). We discovered that the user had used a custom list instead of an events list and we never resolved the issue. We left it to see if it continued to happen and the alternatives were to recreate the list in an events list or to call Product Support.

So I assume no one has access to delete your events? This isn’t a case of someone deleting something they shouldn’t be?

That conversation sure sounds similar to a few I've had around here about this issue...;)

This is a calendar  list, or at least it started out as one. We have customized it by adding columns. I actually "repaired" this at one point by creating a NEW calendar list, re-adding the columns, and creatively importing the data into the new calendar list.

Is it possible that the list is "forgetting" that it is a calendar somehow, and therefore it quits behaving like one? What we're really seeing is a failure of the calendar specific parts (the recurring meeting function, for example) while the regular list parts continue to work  fine. What would corrupt the Webpart in this way? More importantly, how would I detect and stop it from happening?

As for the item deletion--most users are contributors and can delete items. That has never been an issue with other Webparts. I could turn off that level of access, but I would rather have the users manage this calendar on their own.

In my opinion a common problem with SharePoint is “too many cooks in the kitchen”. When you open up a site and content for multi-person editing and control, weird stuff happens. It is the power of SharePoint, yet a major cause for unexplained phenomenons

If you can determine that the list is doing this on its own and it was not caused by fat fingering by a user or mistaken actions by a user, then possibly your best bet is to call product support. Perhaps someone else will have a suggestion, but it seems that if a problem crops up with a canned list/web part (as opposed to a custom web part you develop) it is very difficult to troubleshoot and explain. At least that is what has happened in the past.

I would look at the record sets that are allowed to be displayed in this webpart. I found that the default was around 100 events then everything else disappeared. to fix this I increased the limit to 500 and now it shows fully populated.

When I always want to see all the items on a list I typically bump the
limit to five nines (99999). That way I always know what I was intending
to do with that limit.

Of course, unlike the LVWP, the DVWP has the option to show all
listitems. I use that option rather than the five nines when using the
DVWP.