AFAIK Charter do not block ports ISP's known to BLOCK or Filter p2p or specifically Limewire what they do is shape the p2p use of heavy users. They choose them as they become noticeable as heavy users of bandwidth. It comes under their fair use policy.

Perhaps you may have come under such notice & they shaped you just temporarily. Perhaps as a warning. With their devices they can not only shape the p2p bandwidth, but they can also block your p2p programs from connecting if they choose to do so. They can apply it to specific programs or inclusively. I guess depending upon p2p protocol, ports, etc.

I'm having the same problem. Mine was working fine when I had a cable modem, but then when I switched to a dsl wireless modem, I can't connect to limewire or frostwire. I've tried all of the firewall tricks, and I only get the first bar when connecting. I have no idea if my modem has a firewall, or how I would access it if it did. My dsl provider is verizon, when it was comcast, all was fine.

Look here to see if you have to [configure your DSL modem] too.