http://kb.mozillazine.org/Issues_with_Firefox#Downloading_opening_or_saving_files

Some problems occurs when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

As a test, disable your protection programs and try a download.

managed to get the time left back for the downloads by updating my security software that now supports windows 10. But still can not get my downloads to lock. Almost every time I start a download, it will start at maybe 8 kb, I pause then resume the download, and it will go to 5 mb then drop off and go back to 11 kb and if not caught the download will fail. Try the same download on a computer I have with XP and no problems at all which was the case also when I was running 8.1 had no problems locked in and completed task.

Do you have a monitor or something that shows you what the internet data is doing (sending / receiving bps)?

Do a search for a test program called SpeedTest to check.

Start Windows Internet Explorer. Does it have the same problem?

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?