I have discovered through Google searches that google has accessed pages within limited access forums on my site.

It lists the information as a "print page" or "print view".

The page was only on a forum with a half dozen persons having access and clearly shouldn't be able to be accessed by google searches.

Should this be happening?

Is it a problem which is solved by newer upgrades? ie later since v6.5.5

Thanks.

6,5 is so old I could not tell you.
But there could be a leak.

You could try using a robots.txt rule to block access to pages that you don't want listed in search engines... But as Ruben said, it's pretty old and I don't even have a working copy of it installed anymore to be able to really look it up

Go here: http://www.robotstxt.org/

that's not the issue, i know how to use the robots.txt, the issue is i dont have access to an anciently old ubb install...