well, one should find BW_Herbs\Scripts\AR4800e.baf and add Continue() to it so that it would look like:
CODE
IF
Global("BW02_HerbAddinNashkel","GLOBAL",0)
THEN
RESPONSE #100
SetGlobal("BW02_HerbAddinNashkel","GLOBAL",1)
CreateCreature("BW02CRE3",[823.78],12)
CreateCreature("BW02CRE0",[235.3663],0)
CreateCreature("BW02CRE1",[308.3620],0)
Continue()
END
Or, just unpack this archive into bg2 folder to replace the script with the fixed version