The solution was merely simple. I just found found that Spookie's SCM hook was giving Weapon_Index as parameter to REQUEST_MODEL and IS_MODEL_AVAILABLE opcodes, which was causing the goddamn error. They actually take MODEL ID as parameter.
I made replacements and here is the updated versions. Simply replace them with the old files.ScriptClasses.cppScriptClasses.hGameDefines.hMissionThreads.cpp
Have fun with OOP style Mission coding. EDIT:
I have added a marker next to the original The Sample mission just for the sake of debugging. It just spawns a FBI and a vending machine so it may not be of any use. This post has been edited by Swoorup on Saturday, Jan 21 2012, 13:56