Hi sladoux- I would suggest deleting the file that is corrupt, first of all. Secondly, I would download the latest Firefox build here:

http://www.mozilla.org/en-US/firefox/new/

Hope that helps!

It is possible that your anti-virus software is corrupting the downloaded files or otherwise interfering with downloading files by Firefox.

Try to disable the real-time (live) scanning of files in your anti-virus software temporarily to see if that makes downloading work.

See "Disable virus scanning in Firefox preferences - Windows"

• http://kb.mozillazine.org/Unable_to_save_or_download_files