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

If the file from magnetmix downloads really slowly, it could point to your ISP being the problem. Use the forum search to look for SuddenLink & you might find some other threads where users have the same problem.
Also see these...

http://text.dslreports.com/forum/remark,17082272
http://www.broadbandreports.com/comments/2652?1=1&p=2

What port did you change to? Try one in the range of 49152 - 65535 (eg 64049). Although if this is an ISP issue, there's no guarantee that changing ports will help.