Not sure about Overlander but Outerlimits is up and running. They seem to change the IP address (behind the
www.outerlimits4x4.com/phpBB2) of the actual forum page quite often and shortcuts don't cope with this very well. It is generally worth trying just
www.outerlimits4x4.com and wait for the redirection.
All that being said . . . it seems to be unstable at the best of times so it might just be down.