Using Speedtest.net I've noticed that Firefox is running at around 6meg, whereas other browsers run at the correct 20meg.
Any ideas what could be wrong, as this never used to be the case.
You can try to uninstall some Add-ons, clearing your history and cache and browsing with less tabs.
I've been doing a bit of testing. If I restart in safe mode, it works as it should, full speed. But I've tried disabling all the add-ons manually, and it's back to a third of the speed. Weird!!