ok you can try getting firefox from their FTP site using the ftp command in command prompt, have a look at this screenshot:
these are the steps:
1. open a command prompt
2. type "ftp releases.mozilla.org"
3. when asked for user type "anonymous"
4. for password leave empty and hit enter
5. once logged in type "cd /pub/mozilla.org/firefox/releases/3.5.1/win32/en-US
6. change local destination directory, type "lcd c:\" this will make the destination directory c:\
7. now type---> get "Firefox Setup 3.5.1.exe"
, don't forget the double quotes or the download will not work because the file name has spaces in it.
8. wait for the file to finish downloading, it's 8MB, there is no indicator but when it finish it will say completed.
9. once completed goto destination directory, in our example it's c:\, find the "Firefox Setup 3.5.1.exe" file and run it to install hope this helps! EDIT: Corrected the directory it's en-us not en_US!