Still classing the online "feature" as a bug, more so because it doesn't work, and still stops you from playing.
*Updated* The one here previously caused errors with some door switches, this one does not cause that.
1. Install the game from the DVD.
2. Download the fix here:
Mirror 1: http://www.megaupload.com/?d=8PQCR71I
Mirror 2: http://www.4shared.com/file/y32y5YDP/PoPTFS-SKIDROW.html
3. Go to the game's install directory (usually C:\Program Files\Ubisoft\Prince of Persia The Forgotten Sands) copy the files in the zip into there. If asked to replace files select "yes" or "ok".
4. Now this is optional because it doesn't really matter too much. If you want a certain name to be displayed in game as your name, edit the skidrow.ini and put the name in there where it says username.
Thats it. You can now play the game without the internet.