Download a file from here & see what speed you get
http://www.magnetmix.com/video.shtml

If Charter is the problem, there's not too much you can do. Have a look through the thread below, might be something there although it's probably more for people whose ISPs are blocking rather than shaping.
A Fix for those whose ISP's block Limewire

Some ISPs shape at certain times, their 'peak' hours...try downloading at different times of day & see if there's any difference.
Do other people there use LW? If so, find out what they've done to get it working.