Would you mind doing two things (this seems to be a recurring issue with F-Secure right now): Type about:support into your address bar, press enter. Copy and paste all of the information in there into this thread.

Then, try to Reset Firefox, Refresh Firefox - reset add-ons and settings, and, then see if your download speed is faster, even with F-Secure enabled.

Application Basics

       Name
       Firefox

       Version
       14.0.1

       User Agent
       Mozilla/5.0 (Windows NT 6.1; WOW64; rv:14.0) Gecko/20100101 Firefox/14.0.1

       Profile Folder

         Show Folder

       Enabled Plugins

         about:plugins

       Build Configuration

         about:buildconfig

       Crash Reports

         about:crashes

       Memory Use

         about:memory

 Extensions

       Name

       Version

       Enabled

       ID

       Adblock Plus
       2.1.2
       true
       {d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}

       Browsing Protection
       1.10
       true
       litmus-ff@f-secure.com

       PrivacyChoice TrackerBlock
       2.2
       true
       trackerblock@privacychoice.org

 Important Modified Preferences

     Name

     Value

       browser.cache.disk.capacity
       1048576

       browser.cache.disk.smart_size.first_run
       false

       browser.cache.disk.smart_size_cached_value
       1048576

       browser.places.smartBookmarksVersion
       4

       browser.startup.homepage
       http://www.yahoo.com/

       browser.startup.homepage_override.buildID
       20120713134347

       browser.startup.homepage_override.mstone
       14.0.1

       extensions.lastAppVersion
       14.0.1

       gfx.direct3d.prefer_10_1
       true

       network.cookie.prefsMigrated
       true

       places.history.expiration.transient_current_max_pages
       104858

       privacy.sanitize.migrateFx3Prefs
       true

 Graphics

       Adapter Description
       Intel(R) HD Graphics Family

       Vendor ID
       0x8086

       Device ID
       0x0116

       Adapter RAM
       Unknown

       Adapter Drivers
       igdumd64 igd10umd64 igd10umd64 igdumdx32 igd10umd32 igd10umd32

       Driver Version
       8.15.10.2509

       Driver Date
       8-31-2011

       Direct2D Enabled
       true

       DirectWrite Enabled
       true (6.1.7601.17789)

       ClearType Parameters
       ClearType parameters not found

       WebGL Renderer
       Google Inc. -- ANGLE (Intel(R) HD Graphics Family) -- OpenGL ES 2.0 (ANGLE 1.0.0.1041)

       GPU Accelerated Windows
       1/1 Direct3D 10

       AzureBackend
       direct2d

 JavaScript

       Incremental GC
       1

 Library Versions

       Expected minimum version

       Version in use

       NSPR
       4.9
       4.9

       NSS
       3.13.5.0 Basic ECC
       3.13.5.0 Basic ECC

       NSS Util
       3.13.5.0
       3.13.5.0

       NSS SSL
       3.13.5.0 Basic ECC
       3.13.5.0 Basic ECC

       NSS S/MIME
       3.13.5.0 Basic ECC
       3.13.5.0 Basic ECC

Thank you for that info :)

Did you try the Firefox Reset? It also seems like you have an F-Secure addon installed, if you disable that, does your download speed back up?

Reset Firefox also tried without addons running. Didn't help.

I found this on the f-sercure forums: http://community.f-secure.com/t5/Protection-Safe/Browser-Protection-is-making/td-p/2355/page/6

It looks like it is definitely the browsing protection addon. Can you confirm?

After disabling browsing protection had to reset Firefox to tell any difference. It appeared to speed up browsing but when doing a speed test results seemed very erratic. Example 99.7 Mbps from one site. Other sites the gage animation would not move momentarily and then spike to max speed. Still had to disable f-secure completely to move to higher consistent results on speed tests.