If an error is only happening during the download, not at the beginning of the download then it should not be DNS related. Your OS caches DNS results and JD should not need DNS while downloading a file (once the download starts, the IP address is used, not the Hostname).
It is more likely that your disconnection is due to a problem on the uploading.com equipment. The only way to see that would be to use a network sniffer like WireShark, But I do not understand why this would only be happening to you.
If you are still getting "No permission" messages, check to make sure that no program is reading your *.part files (the incompletely downloaded files). This includes programs that index or catalogue files (such as background searching for media files), antivirus (I know that isn't the problem here), and so on.
Do not forget to use the cleaner program for any antivirus you may have installed and to run a registry cleaner and LSPfix (to check for bad hooks into your network stack -- see
Advanced System Cleaning).