You are saving to a convenient location (e.g., desktop) from the official site: http://www.mozilla.com/firefox ?

How far does it get (e.g., it asks you to name the file, you can see the .part file downloading, etc.)?

Does your security software show that the download was quarantined?

In case this is the result of malware, you may want to run some supplemental scans. These two tools are highly regarded:

Malwarebytes Anti-malware : http://www.malwarebytes.org/products/malwarebytes_free

SUPERAntiSpyware : http://www.superantispyware.com/

Great questions. It takes me to a screen that tells me the server can't find the file. Here is the exact message:

"Safari can’t open the page. Safari can’t open the page “http://mirror.leaseweb.com/software/mozilla/firefox/releases/5.0.1/win32/en-US/Firefox%20Setup%205.0.1.exe” because the server unexpectedly dropped the connection. This sometimes occurs when the server is busy. Wait for a few minutes, and then try again."

I've tried coming from various websites, using various computers and browsers. It still gives me this message or one similar.

Thanks for responding!

Does the FTP server work? ftp://ftp.mozilla.org/pub/mozilla.org//firefox/releases/5.0/win32/en-US/

I tried to download it on my mac but it tells me that some of the data can't be read or written and won't finish the download. I'll try on a windows machine later today but it still seems weird that I can't download it.

Thanks for trying to help!