Fullscreen works fine for me, and I'm assuming there are lots of other fullscreen players. What do you mean when you say "with and without mods?" Is it crashing as soon as you start up or only after a while of playing? I'm not sure what fullscreen would change that would cause Tonberry to crash, but if you're getting "unknown exception" then that does sound like it's coming from d3d9Callback.dll.
I figured it would work fine for other players indeed. And yes I do mean crash right away at start. DId it with blank tonberry and tonberry with mods (e.g. seed reborn) and even with debug on in tonberry and renaming directories to match I get 0 output.
When I start the game in full screen and press play I get a black screen quarter of the screen and 0.1 second later in full screen and it stays black, nothing happens, it has crashed instantly and the popup is hidden behind it to which you need to alt tab. When you press 'ok' on that popup with 'unknown exception' you can get the windows crash that asks to close it etc which also has 0 information. And this happens only in full screen regardless of anything else as long as tonberry is there. In windowed mode it runs just fine with everything working..