Chances are your cable modem is capped at 1.5mbps downstream, 128kbps upstream (like mine). You'll have to ask your ISP what your exact limits are. After you know this, you can try limiting your uploads to somewhere below the limit to make downloading not suffer quite as much.
There is a whole lot of information on this topic, try searching google for "bandwidth throttling", "traffic shaping", or "Quality of Service".
What you describe is perfectly normal for a cable user with typical bandwidth restrictions.
BTW, cross posting in different forums is considered rude. If you have made an error in which forum you posted in, a moderator can correct it for you.
-c
