Slow downloads....sort of.

I wasn't sure how to put it in the topic title.

Basically heres how it goes:

Download something from Megaupload or my personal website via Firefox = 200kb/s and then it starts dropping. It also affects YouTube videos, Ventrilo, and browsing in general.

Download something from Usenet or download something from Megaupload/my personal website using a download manager such as JDownloader or DownThemAll = 1MB/s +

I really can't figure out whats going on.

ADDITIONAL DETAILS

Windows XP Pro (though have tried on Windows 7 and same issue)
Connected directly through Cable modem via ethernet
Speedtest.net has me at 8-9Mbps and thats about what I get with download managers. (obviously the problem being you cant use download managers to browse/view youtube)

 

Found a fix from another topic! My TCP in rate was way too high and apparently that messed it up

 

bump....appears its not fixed.