Hi, Krstfr.
I'm looking at the requests from your clients on the tracker, and I can see the reason why they are failing. In order to authenticate themselves (in case their IP address changes, for instance), the clients will generate a secret key at the beginning of a session. This key is passed along with every subsequent request to the tracker. The tracker will only accept the request if the key matches the initial one.
In your case, and for some reason unknown to me, the key changes for every single request. This seems to happen in both BitTorrent and µTorrent. Very strange.
I'm reluctant to making any changes to the tracker code to permit requests where, for instance, the secret key has changed but the IP address has not. Is there perhaps a third BitTorrent client implementation you could try before we start looking at workarounds?
Also, what speeds are you getting? Your initial request should work, and you should get a list of peers in return on that one. Seeing as the peers on our torrents are pretty stable, I would imagine you'd continue to get decent performance even if your later requests are denied.