Fn+F8 Key / CRT to LCD and Back?

Hi,

I messed with the Fn F8 key on my Inspiron C400 and now when I plug the PC into a docking station and the CRT doesn't work. I then go toggle the Fn F8 key to get the CRT to work. When I undock and boot up the LCD screen does not work. I then go toggle the Fn F8 key to get the LCD to work. I then plug the PC into a docking station AGAIN and the CRT doesn't work. I toggle the Fn F8 key to get the CRT to work.  

The manual doesn't help.

Any ideas?

Thanks.