Franck,
How about click the warning panel ? Does it work ?
For the Flash10 , sometimes we need the users click again , (if the page layout is not compatible with uploader script code)
You can disabled the Flash10 by this way (in the last version)
uploader.SetAdvancedOption(UploaderAdvancedOption.NoFlash10,"true");
So that if the user use Flash 10, it would change to the IFrame mode.
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For the Opera, I think the problem has fixed , please download the control again.
Regards,
Terry