Sorry Jim, I was getting a bit angry little by litlle.
Apparently it has somehow to do with downloading from JRiver. I tried the link that MrC gave me and although I could download it, it took around 15 minutes for a 4,5MB file.
I also tried downloading the trial version of MC (although I already have a registered one), to see how fast that goes. The download goes with 4-5kB/s.
I did both with IE and Chrome as well. No noticable difference.
For comparison I downloaded a trial version of TMT5 from Arcsoft and the 50MB file was complete within 30 seconds !
So throttling apparently occurs but only for JRiver.
Downloading from usenet goes with 56Mbits/s
Btw, AFAIK I don't have special security software. Only Avast and MSSE, both without real-time protection. Moreover, if I had it, wouldn't that influence downloads from other websites as well ?