I also use cable modem and I have the same problem.
Linux will work correctly (including GNOME).
If I understand what is happening, your system is getting this address (dhcp-86-82) from your ISP and, unfortunately, when the system tries to resolve it, it will not find it, because dhcp-86-82 is not valid.
Long story short. I do not know how to correctly fix this issue. I ended up using one of my valid domain names as a hostname for my box. -> Problem fixed.
But not everyone as a domain name.
If you plan on using SendMail locally, every e-mail you send out on the internet will have a return-path: root@dhcp-86-82
, which may caused some problems when some people, not all, try to reply.
If anyone knows how to fix this correctly, please post all suggestions.