Members and admin cannot stay logged in

We are having a very strange phenomenon on my forum and members cannot log in and view certain areas of the site. I am admin and cannot for example see my staff room. This is becoming a big problem and each time I try to access the staff and admin rooms, I am asked to sign in even though I already am and then told the forums do not exist, although clearly they do.

Forum: http://www.reviewwritersforum.co.uk/

Any help you can give would be appreciated.

Rachel

Not sure if my query got lost under others that were posting.

Is anyone answering queries ?