AjaxFileUpload does not work properly outside an Updatepanel

Hi all,

first of all: I´m aware that a ajaxfileupload control does not work inside an updatepanel.

But now to the problem:

I use both controls on a page but the ajaxfileupload is not in an updatepanel.
I want to use a small updatepanel to handle two cascaded dropdownlists without loosing my selections of the ajaxfileupload control by a full postback.

When the page is loaded I have no problem using the ajaxfileupload and selecting files for the upload.
This works perfectly until I select a value of the first dropdownlist and the second dropdownlist inside the updatepanel gets populated via the partial postback. From this event on, the select button of the ajaxfileupload control is without function.

Does anybody know how to get behind that or how this can be debuged?

Thank you very much for your help!