In addition to my previous reply, when I tried java 1.4, my download bandwidth is swinging from 0 to 27KB/s. But most of the time, it stays nearly 15KB/s. This morning, my Bandwidth has a steady state at 14KB/s. I made some experiments and these are the result:
My maximum simultaneous download is set at 8.
1. 14KB/s is shared by 8 simultaneous downloads
2. 14KB/s is shared by 4 simultaneous downloads (4 downloads are paused)
3. 8KB/s is shared by 2 simultaneous downloads (6 downloads are paused). download speed drops maybe due to availability from the hosts.

With these results and from my previous reply, I strongly believe that there is no problem with my LW. As what UK Bob commented, my ISP might be the problem. I'll try to ask some of my friends here using the same LW with different ISP. This might be the answer.