FWIW, I’m not seeing any slowdown using Firefox. Slowdowns in Firefox are more likely to be caused by extensions that haven’t been updated to be completely compatible with newer versions of Firefox.
You may try a repair of Avast via Remove Programs. When the remove dialog for Avast comes up, click on Repair. When it’s done running, restart Windows.
Did the repair option and I did get a download of 2.5mbs but far from 8 to 10 mbs with other browsers.
I don’t want to but I guess I could uninstall Firefox completely and reload but that would be my last option since there is no improvement in safe mode.
It’s doubtful that an uninstall/reinstall of Firefox would change much, as usually the problem lies in the Firefox profile. Firefox Safe Mode doesn’t disable any of the plugins, nor does it correct problems with User.js. In Firefox Add-ons, go to Plugins and disable all of them temporarily.
I too have no download speed issues with avast and firefox 27.0, though I don’t use the avast! internet security (AOS) firefox add-on. But when I was testing the avast versions, I do so with AOS enabled.
If there is no improvement in windows safe mode (if that is what you meant by safe mode), where avast doesn’t run, no Web Shield, no avast internet security firefox add-on and it is those two, if there was an interaction with internet browsing then that is where it would be. What happened when you used IE, should really be the same for other browsers as avast doesn’t differentiate between browsers.
I’m finding it hard to see the linkage and the inconsistency of it working in normal mode with avast off, yet not working in safe mode, when avast doesn’t run is somewhat confusing. Have you tried running firefox with ‘Restart with add-ons disabled’ (firefox menu > Help > Restart with add-ons disabled) ?
If that works then there is a possibility that there is a clash between add-ons (what/where is the problem), what other security based add-ons do you have installed ?
What firefox version are you using ?
I have found that firefox 27.0 messes with a couple of add-ons.