Same here, seriously, as detailed in this thread -
http://cableforum.co.uk/board/showthread.php?t=45349
30% Packet Loss, 64BYTES (yes, BYTES) a second from the Telewest gamefile server at times, Peaked at about 20kbps, shocking. Oh, and corruption.
I have rung Customer Support, i have an engineer out thursday to see what the problem could be, CS fobbed me off with a load of crap "Signal to noise ratio is too high" and i doubt they even know what the problem is.