Detruire: Looking at the behaviour, it's obvious that it's not merely a lack of bandwidth.

I think it could be part of the new Telecom LLU contracts, Slingshot was the first to join, it started at the same time period, the slow 30Kbps limit after 10MB falls into the heavy users 30KBps speed described in the LLU, but that could just be my tin foil getting itchy.It would not be a suprise if that was the new speed of everyones internet.  Look at how religously telecom suck with it's understand of the the 128KBps upload speed that the govt defined.