Mine varies. On a good day, I'm around 250-350 kbps to download, depending on the server on the other end. At bad times, I may be 10-20 kbps.
When you're on cable, you're actually sharing the cable bandwidth with everyone else who's on-line on that network segment -- IOW, your neighbors. If the total pipe is 1.544 mbps, 30 total people brings it to an average of 52 kbps, roughly.
Check your ping times (from command prompt, ping
www.ironworksforums.com). Also check your tracert times (from same place, tracert
www.ironworksforums.com). Ping shows how long a packet takes to get from you to there, but it can time out. Tracert will keep trying, and while it will time out, defaults to 30 hops or attempts. You may go the first ten or more before you get a hit.
When in doubt, call your cable company's support line and lodge a call. It may not help, but it won't hurt, and you may clue them in to a problem they need to address.