Have you installed anything like an anti-virus or ad-blocker recently? The Ad-blocker I used to use had a bug that dropped upload throughput by 50%. I know it sounds a bit weird for an ad-blocker to impact upload speed but they acknowledged it. Something to do with the way they hooked into the network stack apparently.
Apparently they are claiming it's an artefact and not a real figure.
Edited by Andrue (Wed 30-Apr-14 16:07:22)