Hey there ^^ I had this problem once but that was due to me selecting the wrong screen resolution. (I'm unsure about full-screen properties though) Suggesting a solution here. (Worked on Windows 7 btw, Windows 8 should be fine too)
1. Right-click any empty space on your desktop
2. Select Screen Resolution on the shortcut menu
3. Move your cursor over to the "Resolution: (Whatever it says)" option and select it. A slide bar should be shown. Test all supported screen resolutions until you can see the "Options" button on the Onigiri login page.
4. Deslect full screen
5. It should return to normal. Return to your original screen resolution and enjoy.
Hope this works

"I am absolute" -Akashi Seijūrō
Lodging at the
Help and Support Forum. Drop by if you need to ask anything!
Onigiri status: Restarting on wand - Let's see how this goes.
Forum status: On-and-off, on-and-off.