Ubuntu 7.10/VirtualBox1.5.2_OSE/SuSE 10.3 x86_64
I have been playing with VirtualBox on OpenSuSE 10.3 and have been successful with Windows guest but, Ubuntu guest has been irritated me few days by resisting to be full screen mode. I have installed 'Guest Addition' and did everything I have seen from internet forum. But, all didn't work.
Finally, I found out the reason why it is. When I was installing 'Guest Addition', I just clicked the icon of installation script' file and I thought it's done. Today, I opened a terminal window and typed installation script name to run it and it turns out that I should be a root to install it. I've totally forgot about this.
So I used 'sudo' command to run it under root privilege and it works fine now.