You know this problem so sounds much like what I had a few months back. Connection kept dropping randomly, they blamed my computer at first (even though I have 2, and the other one kept dropping too), then they thought it was my modem (i've got the 100 model, 2 years old and still running) then they gave me a new PSU for the modem, thinking it was that, when it was actually a fault in the area since a friend of mine who only lives a few blocks away from me - was having the same problem!
