virtualbox.org

I am currently running Vbox 1.6.4
I would like to upgrade to the latest "safe" version
Which would that be?

Also, if I upgrade, do you have to create the guests all over again?
What are the steps to upgrade?

TIA

You should be able to upgrade to at least version 2.2.4 but you would need to un-install the current version first.
Your guests and their settings should not be lost though but doing a backup is always the safe way to go.
But if everything is working properly and you are not having problem since you are running Solaris as host I would consider staying with what you have or at least don't attempt to go any higher than 2.2.4. I read a lot about people that upgraded their Solaris host and have had problems.