So, everything's working fine as long as I don't download anything. As soon as I start a download, no matter at which speed, my whole internet starts to slow down terribad. For example latency in games increases like hell, almost to unplayability. Websites are loading incredibly slow and so on... Only seconds after I stop the download everything's fine again. I've got an Attansic L1 on-board network adapter, which is recognized as "Atheros L1". Drivers are from Microsoft, as my own don't work.