[jQuery] IE problems with prepend since 1.2.3?

[jody]

IE6 and IE7 since upgrading to jQuery 1.2.3 is targeting line 264 in
the jquery.js (uncompressed) with the error message, "Unexpected call
to method or property access." Here's the bit in jQuery it's
referencing:

prepend: function() {
                return this.domManip(arguments, true, true, function(elem){
                        if (this.nodeType == 1)
                                this.insertBefore( elem, this.firstChild );
                });
        },

Specifically line 264 is claimed to be the culprit: "
this.insertBefore( elem, this.firstChild ); ".

Per usual, Firefox, Safari, and Opera work fine. It could well be my
code that's triggering my latest battle with IE, but I thought I'd at
least ask here. I've spent the last 2-3 hrs or so refactoring, etc. to
see if messy code was causing the problem, but no luck. I consistently
get this same error from the MS script debugger.

Maybe this is something someone else has run into, if so, any help is
appreciated.

Thanks,
jody