jpchatt,
That is expected behavior.
Because when the Flash version >=10 or Silverlight version >=3
The addon do now allow javascript show the browsing dialog.
So AjaxUploader put a transparent layer , and let user click the Flash/Silverlight to show the dialog.
If you tab to the HTML button , it will fire button.onclick , it can't show the dialog.
So we can only show a warning panel , and try to let user click the Flash/Sliverlight again.
(Right click the button or the warning panel, you can see Flash/Silverlight menu)
If you want to avoid that issue, you can set
UploadAddonButtonMode="Replace" (ASPX CODE)
Uploader.UploadAddonButtonMode= UploadAddonButtonMode.Replace; (C# CODE)
Regards,
Terry