i still get this problem regardless of time of day.
having changed routers and even removed the router from the setup i still get the issue.
tried 2 different network cards on my pc and tried my laptop (wired) and still get it.
if it was always doing it id be able to phone up and say something but its a bit random but it does it often enough that i notice it.
started a download last night at 1 in morning went to 6MBs then after 5 mins that dropped to 2 or so
having changed providers for newsgroups its not astraweb.
i also get slow (compared to what my line should do) from other sources and speed tests always come in at under half teh speed it should be.
i was much better off with 20meg service