When I try to download something using OS X, the download doesn't begin or it times out after loading only half-way. When a software like iTerm tries to download its own update, it usually times out, and when I try to download things through the browser, it times out or never begins.
When I try to watch a video on a site like Youtube or Dailymotion, the video does not completely load. If I reload the web page, it loads a bit farther each time, so after two or three refreshes (F5 on Firefox), I can watch the entire video.
On the same machine at the same sitting using the same network connection, if I start up my Parallels VM of Windows XP, I can download these files and watch the videos with no problem at all, so I am sure the cause is somewhere in Mac OS X. This began when I installed Leopard in this computer.
I have already tried fixing permissions.