I think the problem started about one week ago when I upgraded to Firefox 28, at least I didn't notice this behavior before. I'm using the addon Flashgot and the Free Do… (tuilleadh eolais)
I think the problem started about one week ago when I upgraded to Firefox 28, at least I didn't notice this behavior before.
I'm using the addon Flashgot and the Free Download Manager to manage my downloads. However recently with certain servers (which I had been using regularly for years without issue) FDM would start the download but it would sit at 0% for a while and then just switch to pause on it's own. I got a message that's because the server only allows one download at a time and there was already a download going on which I didn't know anything about. I also noticed that even the servers that worked were downloading a lot slower than they did usually and web usage in general was slow. I checked what was going on with a program called Netbalancer which showed that Firefox was constantly using up lots of bandwidth even though there were no webpages or videos loading and there was nothing showing up in the integrated download manager. I tried to close Firefox but that didn't fix it either. The same amount of bandwidth was being used now listed by Netbalancer as Service Traffic.
That happens every time I download anything on the web. As soon as the download dialogue window comes up Firefox apparently already starts downloading the file in the background even if I decide to just close the window or use FDM instead. It doesn't show up in Firefox's download window and there is no way to stop the download other than doing a reboot or waiting till Firefox has finished downloading the file even if it takes several hours!
So far I've tried upgrading to Firefox 29, downgrading to 21 which I used before, deleting my Profile, doing a clean install of 21 and checking my system for malware with several tools but nothing helped. I also tried downloading the same files with Internet Explorer+FDM and it worked without problems.