I too am unable to access this function. When I want to read 'unread posts since last visit' I point to that line and it is underlined in white - click and I'm in. This is not happening in the 1hr etc.
I see sandgrounder is also having oroiblems but he (she) did not elaborate. I've put off querying this expecting somebody else to raise the issue - then I wouldn't look stupid perhaps I'm having a senior moment!