First of all, thanks to everyone trying to help out. I'll file a problem report when I find the time and hope that this will help with my constantly slow WiFi issue.
@CindyOr: I can really understand your pain and I think you are absolutely right. Microsoft has to work on customer support. Sometimes, it feels a little bit like they are trying to keep you busy until you give up. ;) And sometimes it seems that they know more than they want to tell. But that is just a personal feeling…
Cheers,
Tim