I had the same problem with several servers, and I got it right by extracting the recvpack form the client
All you have to do is follow this guide:
http://www.openkore.com/index.php/Recvpackets.txt
once you get the recvpackets, exchange it on your iRO folder or kRO folder (bot/tables/iRO)
it always works for me
If the JCV tools do not work (some clients are patched) you should try using this:
http://forums.openkore.com/viewtopic.php?f=36&t=13305
It is more difficult, but it works
After all this your openkore should run perfectly