Hello, can you help us with some information. Did you see this issue with the previous version of Firefox? That can provide us clues on where to look.

Thank you

Could you try this?

1. In the Location bar, type about:config and press Enter. The about:config "This might void your warranty!" warning page may appear.
2. Click I'll be careful, I promise!, to continue to the about:config page. A list of settings should appear
3. Filter the list by typing in the search bar at the top. Type in scanWhenDone. You should now find the "browser.download.scanWhenDone" preference.
4. Double-click on that preference to set the value to false.
5. Next, try to download something and see if it still hangs.

Please reply and tell us whether this helped you!

If it doesn't work, reenable the pref that was disabled.

The problem existed previously, it went away briefly, and recently returned. I did just upgrade to 25.0.1.

The "browser.download.scanWhenDone" key doesn't exist.

Edit: "browser.download.manager.scanWhenDone" exists, however.  ;) I set value to false. This appears to fix the problem.

Hopefully that doesn't disable antivirus from scanning FireFox downloads? (It would appear to be a bug, either way.)

Thanks for the help.

Hi kmfx, setting the browser.download.manager.scanWhenDone preference to false means that Firefox does not submit the download to Windows for scanning, and does not mark the file as having originated from the internet. (Some programs handle files with that flag different, by opening them in a protected mode, for example.)

There's still a reasonably good chance that your regular, full-time/real-time security scanning will check the file. However, if you're not sure, you could test using the EICAR test file. This is a non-malicious file that security companies use to verify whether a scanner is running. More information: http://en.wikipedia.org/wiki/EICAR_test_file

jscher, that was highly informative, thank you. I'll test it, and let you know. My concern is that disabling the flag could have other unconsidered consequences on various computers (test of AV, or not). Will devs consider this a bug/security risk to be addressed in future release?

I'm not sure why the files disappear when they are marked as downloads from the internet -- that's not the normal behavior. I don't recall researching this problem in enough detail to have a theory, but my suspicion -- if there is no malware active on the PC when it occurs -- would be "something" having changed a registry entry that affects download policies.

By the way, does this only affect the Save option, or does it also affect the Open option? The main difference from the downloading perspective is that Open always uses the Windows TEMP folder, while Save will use whatever folder you designate.

You can't open a file that isn't on the computer. As soon as it downloads, it disappears. A search for the file indicates that it isn't on the computer--temp, anywhere. You can't even get the "open containing folder" option to work. I'm not clear on what is causing the files to disappear but the common denominator is Firefox and its preference settings.

Hi kmfx, I guess my question wasn't clear. When you click the link, and Firefox displays the dialog with the choices of Open or Save, does Open fail as well?