******* script runtime error *******
undefined is not a field object: (file 'maps/mp/gametypes/_weapons.gsc', line 312)
  if(getCvar(level.weapons[weaponname].server_allowcvar) == "")
                          *
called from:
(file 'maps/mp/gametypes/dm.gsc', line 88)
 thread maps\mp\gametypes\_weapons::init();
        *
called from:
(file 'maps/mp/gametypes/_callbacksetup.gsc', line 15)
  [[level.callbackStartGameType]]();
          *
started from:
(file 'maps/mp/gametypes/_callbacksetup.gsc', line 10)
CodeCallback_StartGameType()
*
************************************
writing to: D:\Games\cod2\servercache.dat
Error during initialization:
script runtime error
(see console for details)
(file 'maps/mp/gametypes/_callbacksetup.gsc', line 10)

I have a gsc and arena file.

Could you post your .gsc?

ah iv seen this before although u didnt tamper with that at all im guessing ur adding a weapon to another team or somthing or even adding a custom weapon normaly u either
A. Precacheing a weapon and spelt it wrong or somthing
B. adding your weapon to this list here and u numbered it wrong or spelt it wrong so please check that.

level.weaponnames[19] = "mp44_mp";
	level.weaponnames[20] = "shotgun_mp";
	level.weaponnames[21] = "fraggrenade";
	level.weaponnames[22] = "smokegrenade";

C. adding your weapon like this and u spelt somthing wrong or could have added level.weapons[]; above it this is what u should have as an example

level.weapons["m1carbine_mp"] = spawnstruct();
	level.weapons["m1carbine_mp"].server_allowcvar = "scr_allow_m1carbine";
	level.weapons["m1carbine_mp"].client_allowcvar = "ui_allow_m1carbine";
	level.weapons["m1carbine_mp"].allow_default = 1;

And if its none of this and i was completly wrong then feel free to make me look like an idiot and post ur script

It was a mod that was screwing it up. Problem is now, it won't play any updated version I compile and run from compile tool.

are u adding ur b3dbsp into ur .iwd after u compile again?

Yes. I thought that when you run from the compile tool you didn't need to update your map .iwd