What does speedtest.net normally say, and how are local downloads just to make sure it isn't actually your line but rather international bandwidth. Which you can't do anything about really..
There was a post about this last week, myself and a few others had the same problem....around the 20th last month my line still connected at 4096 but could not dl anything faster than 54k per sec. It is still like that. And no one on the forum as any idea why the lines are doing this. Mine was tested across all packages, IS and SAIX. Same Result.
430k/sec down to 50 odd K per sec....like driving a ferrari with a beach buggy engine.