IE js error in filebug

Further details:

It is an error produced by the page shown after you enter a summary for a bug.
(Where you are prompted 'Do any of the following bugs describe the bug you're trying to report? ...)

Having the error prevents the 'No, I need to report a new bug' button working.

I get the same behaviour if I start the bug raising workflow (using the 'Report a bug' link) from either:

 https://launchpad.net/bzr-explorer

or

 https://launchpad.net/bazaar

I'm having a user report a very similar error with Internet Exlorer 8 as well on a different project when trying to report a bug.

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; WOW64; Trident/4.0; SLCC1; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 1.1.4322; .NET CLR 3.0.30729)
Timestamp: Sat, 6 Mar 2010 19:27:15 UTC

Message: Object doesn't support this property or method
Line: 662
Char: 105
Code: 0
URI: https://launchpad.net/+icing/rev9078/build/launchpad.js

From a duplicate on 2010-09-16:

*********
Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; .NET4.0C; .NET4.0E)
Timestamp: Thu, 16 Sep 2010 04:35:45 UTC

Message: Object doesn't support this property or method
Line: 556
Char: 108
Code: 0
URI: https://bugs.launchpad.net/+icing/rev9766/build/launchpad.js
*********

I think there is a second manifestation of this bug. When there are no matches, the text area to provide details does not appear. The automatic action to show the text area fails just as the manual action called from the button.

I believe the issue is in filebug_dupefinder.js show_bug_reporting_form() specifically
    var bug_reporting_form = Y.one('#bug_reporting_form');
looks suspicious because that id is not valid css.

wgrant testing with IE8 identified that event.stopPropagation() is being called. IE does not support that, but YUI /should/ we be adding that (probably to set event.cancelBubble = true). dragscroll.js and pofile.js also call stopPropagation(), They may be broken.

IEEventFacade is not being correctly installed, despite its inclusion in launchpad.js. This also affects production.

wgrant discovered that the event facade is not being loaded. I see that other Lp JS uses event.halt() to do both stopPropagation() and preventDefault().

critical per zero oops policy

Fixed in stable r13202 <http://bazaar.launchpad.net/~launchpad-pqm/launchpad/stable/revision/13202>.