Hello there.

Well, first off, you need to see if this issue is just with Firefox or if it's present on other browsers as well. Try Internet Explorer and see if it has the same issue. If it does, then it's not a problem with Firefox, but with something else, and, unfortunately, I can't help you with that. You should either contact Microsoft for support or get someone there to physically access your computer and clean it up a bit (if that's the problem). I can recommend you to uninstall any and all programs you don't need, to disable any and all startup programs you don't want, not to use more than one anti virus (but do use one), not to use more than one firewall (but do use one) and to check your computer for malware. There are plenty of malware scanners on the web, here are some:

• Malwarebytes' Anti-Malware - malwarebytes.org/mbam.php
• SuperAntispyware - superantispyware.com
• AdAware - lavasoftusa.com/software/adaware
• Spybot Search & Destroy - safer-networking.org/en/index.html
• Windows Defender - microsoft.com/windows/products/winfamily/defender/default.mspx
• Dr. Web Cureit - freedrweb.com/cureit

Also, I recommend you install and run CCleaner, a free computer cleaning software that's very easy to configure and has some neat interesting features. Don't forget to instruct it not to delete your browsing history and so on when you first use it (aka read the on-screen instructions and option boxes).

All this is better done by someone experienced, but an unexperienced user who knows the basics of Windows usage shouldn't have much problems doing it.

If the problem is not present on Internet Explorer, however, then it's possible that you are having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?

Whenever you have a problem with Firefox, whatever it is, you should make sure it's not caused by one (or more than one) of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode (don't forget to select Disable all add-ons when you start safe mode). If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and themes and this one for plugins.

If you need support for one of your add-ons, you'll have to contact its author.

If the problem does not disappear when all add-ons are disabled, please tell me, so we can work from there. Please have no fear of following my instructions to the line, as all can be easily undone.

Morbus I'm having the same problem. On my computer if I use IE I get 30 Mbps down and 6 up which is what I pay for. On Firefox I'm getting 4-6 up and 2-3 down.

I did all the steps you outlined above and nothing made a difference?

Thanks

Can you please try it in a new (temporary) Firefox profile and see if the issue is still present? See this article to know how to create a new Firefox profile. Please report back the results.

Which security software (firewall) do you have?

Another possible cause is security software (firewall) that blocks or restricts Firefox without informing you about that, possibly after detecting changes (update) to the Firefox program.
Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox.

See Server Not Found - Troubleshoot connection problems and Configure firewalls so that Firefox can access the Internet and http://kb.mozillazine.org/Firewalls

No Firewall

New profile made no difference.