RS2005 Date Parameter - JScript Error

I have a RS2005 report that was deployed to a ReportServer and has been running for over 1 month. I personally have not run this report in the past month, however, today when I tried to run it I got an error trying to select a date parameter. I can't paste samples of the windows displayed, so I'll do my best to explain. When I click on the report, it goes to the View window and displays 2 date parameter fields. When I click the icon next to one of the parameter fields, I get an error window that says
A Runtime Error has occurred.
Do you wish to Debug?

Line: 383
Error: 'resultfield.id' is null or not an object

I click Yes and get a VS Just-in-Time Debugger window, where I choose New instance of VS 2005. When VS2005 opens, then I get this error:

Microsoft JScript runtime error: 'resultfield.id' is null or not an object

The Continue option just keeps displaying this error, when I click Break it shows me the code below and has highlighted the line I show in BOLD:

function ClickDay(date)
{
var win = document.parentWindow;
if (!win) win = document.contentWindow;
if (!win) win = document.defaultView;
if (!win) return true;

var ifrm=win.frameElement;
if (ifrm==null)
{
return MoveToDate(date, false);
}
var eltValidator=win.parent.document.getElementById(ifrm.resultfield.id+g_strDatePickerRangeValidatorID);
if (eltValidator !=null)
{
eltValidator.style.display="none";
}
var OnSelectDateCallback=ifrm.OnSelectDateCallback;
OnSelectDateCallback(ifrm.resultfield, date);
var resultfunc=ifrm.resultfunc;
resultfunc(ifrm.resultfield);
return true;
}

To make this more confusing, after I get this error a few times, eventually it lets me choose a date and run the report. Another quirk of my PC is that I often get runtime errors that ask me if I want to Debug when I'm in IExplorer.

Any idea what is going on and how to fix it?
Thanks in advance!