I have almost same problem, but that solution didn't help. And my mod is completely original, so I haven't changed anything. Before RC5 everything worked fine on the way how they are now (file locations).
******* script runtime error *******
cannot cast undefined to bool: (file 'maps/mp/_flashgrenades.gsc', line 3)
if(level.ex_teargas) precacheShellshock("radiation_high");
*
Error: called from:
(file 'maps/mp/gametypes/_weapons.gsc', line 86)
thread maps\mp\_flashgrenades::main();
*
Error: called from:
(file 'maps/mp/gametypes/_globallogic.gsc', line 3739)
thread maps\mp\gametypes\_weapons::init();
*
Error: called from:
(file 'maps/mp/gametypes/_callbacksetup.gsc', line 15)
[[level.callbackStartGameType]]();
*
Error: started from:
(file 'maps/mp/gametypes/_callbacksetup.gsc', line 10)
CodeCallback_StartGameType()
*
Error: ************************************
********************
ERROR: script runtime error
(see console for details)
cannot cast undefined to bool
********************
----- Server Shutdown -----
Sending heartbeat to cod4master.activision.com
==== ShutdownGame (1) ====
Edit: It happens only after execing the server.cfg (which execs the rest .cfg's). And after changing map, restarting, etc.