Banned from a Website what to do?

the final suggestion is try to reformat your PC and try to restart your router,, hope it can help

well, this is a pretty old thread and more than likely OP solved the issue by now or moved on, but here's my insight:

i think OP is referring to imvu and they have a chat client, if OP says he can create accs through the web interface, then there's no problem with his IP or cookies after he's done with the changing/cleaning
imvu must track him through their client somehow right after he logs in, so he either needs a fresh install after completely removed all traces from the registry, he can also try another windows profile, if it doesn't work, he can still use virtual machine or an entirely different machine, many options to choose from