By "change the filter" do you mean modifying a value referenced in the filter expression?
Yes, a different portal on the same layout offers the options to filter the main portal for different values.
Thanks for your interest.
A web browser does not exchange data with the hosted database as frequently as does a FileMaker Pro client application. If you are using buttons in that portal to perform scripts that modify the fields referenced in the filter expression, include a commit records step to submit the changed data back to the database.
If you are using script triggers on your layout, be advised that you cannot directly "trip" a script trigger from a Web browser client.
Thanks for the suggestion -- alas, it didn't work. But in checking it out I made an accidental discovery: that the privilege set in use affects the outcome. If I log in as admin I get the problem. If I log in as a regular user with a fairly restricted set of rights, it works just fine. That is to say, it's the opposite of the normal problem one encounters with security settings.
I shall investigate this in detail tomorrow and see if I can find an explanation...
I'm grateful for your assistance.
OK, here's what I did. I made a new privilege set with everything enabled (ie a close analogue to the Full Access set). A user with those permissions gets the error about the date, just as admin does. I then made one change to deprive that user of the ability to edit, create or delete records in the table in which the date field resides. The problem goes away.
I also did some testing with layouts. I made a layout that mimics what's in the portal. I can edit the record there both manually and by using the scripts on buttons as in the portal. But if I switch back to the portal I get the error again.
So the fault appears to be confined to a portal in IWP (remember, everything works fine in FM Pro), and affects only users with permission to modify records in a related table but not those without. It's a mystery to me why the portal makes all the difference.
In practical terms I can live with this as it only inconveniences administrators not users and then only when admin is using the browser not FM (ie hardly ever). But it's annoying nevertheless, and may represent a bug that FileMaker needs to look at.
Many thanks for your help -- you do sterling work here. I will file a report as you suggest.