Those symptoms usually mean that you can't get a stable connection to our main server. The game can make a connection, but then there's too much packet loss to transmit anything, and the connection breaks. The game keeps retrying though, and eventually one of the unstable connections manages to generate some invalid data before hanging up. (That's what the 256 error is, a corrupted game packet. It's generally a symptom of the same problem as the constant disconnect/reconnects.)

Typically this means there's a hardware problem with your internet connection. If you have 100% reliable connection to the rest of the internet, then it could be a routing problem between your ISP and our ISP, which we can talk to our ISP about fixing... but if your internet is generally flaky, the game is probably never going to be usable for you, I'm sorry to say.

We'd usually recommend reinstalling the game at this point, to rule out version problems or corrupted downloads, but you've already done that. Please try the verifier in the launcher, though: run the launcher, click "Options..." instead of the Login button, then press "Validate Installation". If you still have problems after that, I would really suspect it's not a software problem at all. (If it was a problem with your firewall, you wouldn't get any connection at all.)

(Edit: were you the person that sent in your log file via email? I remember seeing a log about a similar situation, but the log file just described problems keeping a connection to the server; it didn't have anything more specific.)