I don't think it's an ICQ problem.  I've cable as well (Rogers@Home in Brampton, ON.) and at certain times, usually in the evening, I will sometimes get 5K transfers over ICQ as well.  Most of the time though I'm in the high 40K area.  Anyways, it's probably not an ICQ problem but rather a problem with your ISP.
Maybe they are doing upgrades to their servers.  I know that for two weeks straight Roger's was upgrading in our area and the internet sucked big time.  Worse than dial-up.  UGH!  But all is fine now.