Can anyone help?

Are you using any scripts that change the default font?

Yeah, but I just tried removing it and the dialogue still isn't showing up.

Well it is probably something with the scripts. Try to change the color of the text with the \C[#] command and see if it shows up then.

Which scripts are you using?

EDIT: Wait, it don't show up in the editor either?! Then it isn't a script error. Reinstalling VX would be the best then.

In your Window.png you don't have a color for normal text, maybe.

Oh yea, that is true. Try to change back to the original windowskin.

I have had something like that happen to my game...
If you Save your game while many processes are running it will corrupt it.
I have had these things happen (I also removed all other than base script):
Not being able to press down
Not being able to move
A black screen
A error saying "Actor data not found"
A constant error saying "You have not set your default position"
A error saying "SyntaxError at Line 8: Graphics.freeze"

Changing back to the original Window.png fixed it. Thanks for your help! What in the picture represents the text color?

the small white box in the right hand corner.