After a lot of googling, I managed to install the Guest Additions onto openSUSE running on Sun VBox. But after I did that, I wasn’t able to connect to the internet from Firefox.
For some reason “browse offline” was turned on. I turned it off from file>browse offline. Then, when I refreshed the page, Firefox told me to check my DNS settings.
Before I installed guest additions, I was able to use Firefox easily through openSUSE.
My host OS is Mac OSX Leopard, and the openSUSE interface is gnome. Also, I am connecting through Wireless