When you create an RA account, you're actually making 2 accounts with the same username and password. One of these is for the forums, and the other is your RA account, which currently does basically nothing, but has a ton of stuff coming in future releases (a new xp system, some kind of guild system, some tools, etc.).
Currently, although the signup script creates both accounts, they otherwise aren't linked, which means that when you log into the menu bar, all that really happens is the prompt disappears and you get a logout button. This is, understandably, confusing a lot of people.
This means that yes, logging into the menu does NOT currently log you into the forums as well.
The next release is going to have the beginnings of the RA account actually doing stuff so it's not pointless, and I'm going to try to fully link the logins, so a login on the menubar WILL doubly log you in - although that may be the release after, depending on how hard that turns out to be. (Long story short, the forum has some nice protection to prevent script-based logins (stops spammers), but it's well... blocking script-based logins, including the RA one coming from the same machine.
I need to find a workaround to this, or failing that, I may just disable the check as I can't imagine spammers going out of their way to target us to that extent.)
The next release will be on November 1st if you're wondering.