So issue resolved? If your server is up for long run then commands send through rcon tool wouldn't be responded back because I think there is an issue in ET 3.00. Even I have faced same issue on my hardcore server. But if you use qtracker and connect at same time then you might be sending connection packets more then xx times within xx seconds and hence you are facing that issue. I would suggest to join server first then minimize ET and then start any tool to use rcon on your server. This way you wouldn't exceed packets / second.