Do you use a patched wow exe for removed xml check?
Did you also make the core changes for rhe new races. If you click creat the client ask the server for the race data. If the server dont know the race wow crash.
I think the thing is that you not have 10 races neither 25, instead you have 20. Maybe try it with this number.
To be clearly, what did you change? I'm talking of MAX_RACES = RACECOUNT; line 2 in CharCreate.lua.