form.elements has different behaviour.

While FireFox and Opera pass this check:

!form.elements.nodeType

where nodeType is undefined, Internet Explorer 6 (I don't know about 7) returns nodeType === 1 so I've temporary fixed return value inside init method using this check:

return this.setArray(
	a.constructor == Array && a ||
	(a.jquery || a.length && a != window && (!a.nodeType || a.length) && a[0] != undefined && a[0].nodeType) && jQuery.makeArray( a ) ||
	[ a ]
);