Can you provide a test case? The problem with the old code was exactly that the try/catch swallowed errors in a user's inline handlers, so it sounds like the new code is doing just what it should be doing -- allowing users to see errors.

It is quite hard to get a real life test, because we use the asp.net-framework. But here is a little mockup: http://jsfiddle.net/FAG6m/5/

The change-function has quite a similar behavior as our .net-validators in the internet explorer, i.e. trying to access an collection, which is null.

Okay, then use the IE debugger (F12), turn on script debugging, and find out where the error occurs. The call stack and locals should tell you more about the error.

This is the by asp.net autogenerated function, that causes the problems:

function ValidatorOnChange(event) {
    if (!event) {
        event = window.event;
    }
    Page_InvalidControlToBeFocused = null;
    var targetedControl;
    if ((typeof(event.srcElement) != "undefined") && (event.srcElement != null)) {
        targetedControl = event.srcElement;
    }
    else {
        targetedControl = event.target;
    }
    var vals;
    if (typeof(targetedControl.Validators) != "undefined") {
        vals = targetedControl.Validators;
    }
    else {
        if (targetedControl.tagName.toLowerCase() == "label") {
            targetedControl = document.getElementById(targetedControl.htmlFor);
            vals = targetedControl.Validators;
        }
    }
    var i;
    for (i = 0; i < vals.length; i++) {
        ValidatorValidate(vals[i], null, event);
    }
    ValidatorUpdateIsValid();
}

The _selectDate-function of jquery.ui.datepicker triggers the change-event. Between this function and the ValidatorOnChange-function is the usual jquery callstack.

According to the debugger, in IE the targetedControl is filled by event.srcElement. The other Browsers use event.target.

But it has neither validators nor is a label so the variable vals is not filled and is undefined. So vals.length causes the error. It looks as if the function tries to validate the jquery.ui.datepicker itself, because the targetedControl-variable causing the error has no id-attribute and as innerHtml-attribute the number value of the selected day; e.g. picking May, 25th, you geht as innerHtml 25. I think IE validates all html-elements, that have changed, and that causes the problems.

I debugged with IE9 in Browsermodes IE7-9, but all IEs from 6 to 9 have this behavior.

That seems like a bug in the assumptions of the autogenerated code. The vals variable is not set at all in the case where it fails. Note that code does not seem to be intended to be run under jQuery, it does its own browser feature detects for validation.

In any case, the error does not seem to be anything we should be masking via a try/catch inside jQuery, so I'm going to close this ticket.