User Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:50.0) Gecko/20100101 Firefox/50.0 Build ID: 20161213225121 Steps to reproduce: Hello, I see similar issues reported but none of the solutions of the old issues helped. Also tried asking support question  but I think it's time to move it to bugzilla. It is similar problem to https://support.mozilla.org/bg/questions/1026743 https://support.mozilla.org/en-US/questions/1134063 https://bugzilla.mozilla.org/show_bug.cgi?id=180672 https://bugzilla.mozilla.org/show_bug.cgi?id=171441 Issue is with Firefox 50.1.0 on Fedora 24. Cannot download file from: http://dox.bg/files/dw?a=1abb6d1a24 (captcha only required digits and one has to click on the filename to download). I see: > /tmp/mozilla_avalon0/Tzudza6B.bin.part could not be saved, because the source file could not be read. > Try again later, or contact the server administrator. None of the solutions I could find worked. Restarting, compreg, accept-encoding - nothing. I read also these articles to no avail: http://kb.mozillazine.org/Source_file_could_not_be_read http://kb.mozillazine.org/Unable_to_save_or_download_files Midori browser can download this and other similar files. With the pointers of the people that participated on  I also found out other facts: * in web console I see "The character encoding of a framed document was not declared. The document may appear different if viewed without the document framing it". * Midori downloads the file as `ì5-1_19122016(6).pdf` while it is listed on the site as `м5-1_19122016(10).pdf`. This makes me thing that could really be an encoding issue. * At the time error window appears, I really can copy the `.part` file. And it appears to have correct content. So issue is obviously in the code that should rename file back to the original filename. I can't understand why error happens before I have a chance to select a filename. I have configured firefox to ask me before downloading stuff but I don't have a chance to select what action do I want. It would really help if somebody can look at the file soon. I don't know how long the file will stay on the server and it might be impossible to reproduce after it is gone.  https://support.mozilla.org/en-US/questions/1151858
FYI running firefox with a clean profile also did not help.