You will need to be quick to do it ...
When you run speedtest.net there is a small graph just below the instantaneous speed ... using <Alt><PrintScrn> can you capture that, use Paint or similar to remove the IP address (but not server) and host the image on Photobucket or similar.
Also if you use the TBB flash based speedtest
http://www.thinkbroadband.com/speedtest/broadband.html there is a graph there too.
One of those graphs may give an extra insight into the potential issue.
Also,
You have posted the software version, can you get the Hardware version too: http://home/xslt?PAGE=C_0_0 it will be in the format 2701-100630-nnn
Can you create a Quality Monitor for your connection ...
http://www.thinkbroadband.com/ping/monitors/create.html and after a few hours post a link to the "Share Live Graph"
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