Jquery, blockUI. Problem in IE 7,6.

Question

Ok when I'm calling $.blockUI in Internet Explorer 7 it gives me javascript error:

Object doesn't support this property or method

When I lunch Firefox in IE 6 mode with firebug it tell me that

s.setExpression is not a function

this code is in blockUI javascript.

I dont understand... maybe it is conflict with jquery? Becose whrn i run it in the official site it works fine. Or maybe the problem is whith css?

My code as simple as:

$.blockUI({message: $("#popup_lists")})

The plugin is here http://github.com/malsup/blockui/raw/master/jquery.blockUI.js?v2.31

Exception is in this function:

    $.each([lyr1,lyr2,lyr3], function(i,o) {
        var s = o[0].style;
        s.position = 'absolute';
        if (i < 2) {
            full ? s.setExpression('height','Math.max(document.body.scrollHeight, document.body.offsetHeight) - (jQuery.boxModel?0:'+opts.quirksmodeOffsetHack+') + "px"')
                 : s.setExpression('height','this.parentNode.offsetHeight + "px"');
            full ? s.setExpression('width','jQuery.boxModel && document.documentElement.clientWidth || document.body.clientWidth + "px"')
                 : s.setExpression('width','this.parentNode.offsetWidth + "px"');
            if (fixL) s.setExpression('left', fixL);
            if (fixT) s.setExpression('top', fixT);
        }
        else if (opts.centerY) {
            if (full) s.setExpression('top','(document.documentElement.clientHeight || document.body.clientHeight) / 2 - (this.offsetHeight / 2) + (blah = document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop) + "px"');
            s.marginTop = 0;
        }
        else if (!opts.centerY && full) {
            var top = (opts.css && opts.css.top) ? parseInt(opts.css.top) : 0;
            var expression = '((document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop) + '+top+') + "px"';
            s.setExpression('top',expression);
        }
    });