Ouch - you are right. It's a mistake, but not the reason of my problem.
Actually, I think it's not really important if I write something on index position 0 or not.

My panel expects a value of "item_StringID[1]"
The "write_Items" function also changes the variable of item_StringID[1].

But I've also tried to write on item_StringID[0]. No changes. =/

Compiling runs without any problems. There are no errors, when i call the item Menu.
I think there must be another syntactic error inside the script.