Having "all items" can sometimes cause conflicts with essential story items (like the "Sun Badge" or "Blown Mirror"). Try disabling the codes after you have the items you need.
For those who want the most comprehensive tool, the game includes a hidden . Activating it provides access to a vast array of developer tools, including a complete item list. While the menu's text is entirely in Japanese, it is widely considered the ultimate cheat, giving you control over nearly every aspect of the game. suikoden 1 gameshark codes have all items