Ok, I was trying really hard to keep backward compatibility with version 2.1, but I freaked out and dropped it. The new version 3.0 will be completly non compatible with version 2.1. The reason is simple: when I was coding NR, I was using strings as commands. Strings SUCK big time, so I decided to use binary traffic, that is much faster, and using gzip on text, make it even better, and it was not possible with the current way the commands were handled.
I will keep both versions on the site, in case you need to establish connections to older versions, but I really recomend upgrading your existing 2.1 servers to 3.0, and initially, I will make it able to have the two servers installed on the same machine (2.1 and 3.0) so no conflicts will happen, alright?
Since I don't have the forums for any realtime feedback, I created a twitter, you may follow NWC at nukewintercrew (why didn't I did this before???)