Cant read message box - ......just cant see it

[Chyan Guo Messenger]

i clicked on the bag

it opened....i right clicked it again....it opened another 10 slots or something.
i clicked on one of the slots. and there was a messagebox,

but it was unreadable. i couldnt see it.

the game froze too. what is wrong with the screen that i cant see the message box?