Looks to me like you're trying to read information that does not exists or is invalid for the type you are trying to use it as.
Make sure the item you are creating is fully populated (eg: you are setting a proper item ID)
Chances are you are doing something like...
ItemInfo I = new ItemInfo();
if(PercentSuccess(X))
I.ID = MeteorId;
etcetcetc
Chances are you are under certain conditions NOT populating that field and therefor when you try to send the drop it won't actually work.
Basically you need to re-write your drop item code so that it's creating a item properly.