[Alan85]

TreeView1->Items->Add(TreeView1->Items->Item[cat-1],category->ReadString("Item_"+IntToStr(item), "name", NULL)); »

замени на

Код:

TreeView1->Items->AddChild(TreeView1->Items->Item[cat-1],category->ReadString("Item_"+IntToStr(item), "name", NULL));

и будет все ок