Custom GUIs - Adding to Inventory crashes game

[Scavenger]

Lets see. I'm creating a Flight of the Amazon Queen style gui for my game, but whenever I try to add to the inventory, it terminates with this error message:

^ Artists interpretation of the incriminating evidence.

I made SURE that the inventory items fitted within my gui. It was 5 inventory items per line (I set the variable in Game_Start), one line, 33x39 graphics. I calculated this as 165x39. So it can't be the sizing. My gui works until I press Ctrl-S (get all inventory items) or I use Add Inventory. I'm using 320x200x256 colours (apart from the colour loss, it rocks!) Any suggestions? I'm stuck, and this is my first game.

[Scorpiorus]

!Do not alter game.items_per_line variable! Better stretch/shrink a bit  your inventory window (ex: 170x50) ans see how it goes.

-Cheers