Unspecified error when attaching files

A clean install of latest 6.x-dev throws out an "Unspecified error" when attaching files in the node add page. This happens on Intenet Explorer only. The problem is caused by this line in ahah.js:

button.css('float', 'left').attr('disabled', true).after(progress_element);

I split the line into 3 lines:

button.css('float', 'left');
button.attr('disabled', true);
button.after(progress_element);

and I found out that the problem is in the 2nd line, when the button is disabled. This prevents the button to submit the form and there's no response in the target iframe. I added a watchdog in the upload_js() function, to trap the form subit, but it won't show in the log list. If I remove the 2nd line, everything works fine. If I replace the 2nd line with something like

button.css('display', 'none');

it also works fine.

I wrote a sample html form that targets on an iframe upon submit, and I had the same problem: if the button is disabled in the onclick() handler, there's no form submit and the iframe is empty.

I fixed it by setting a timeout to delay the disable:

window.setTimeout('$("' + this.id + '").attr("disabled", true);', 10);

The attached patch fixes ahah.js