Thanks very much for your reply Robkk. I’m glad someone has seen my post and can relate to it a little.
I have tried all the steps through the guide without success. The error still occurs with all other plug-ins disabled, in Twenty-Twelve theme, changing the permalinks to default and in all other browsers etc etc. After clearing the cache and restarting the browser i get the error. However . . .
– If i log in to the site via ‘site.com/wp-admin’, i can access the forum fine.
– Then i log out and log in to the forum, no problem.
– If i close and re-open the browser, i am blocked!