Login - every time?

I'm not sure if this is the right section to post this – but I will anyway.

Every time I leave the Forums without signing out and browse elsewhere on the Web this site logs me out.

And every time I return I have to 'Sign in or Register' again despite ticking the 'Remember my Login' box.

Even leaving momentarily and then returning I get the same response.

My IE settings allow session cookies and override automatic cookie handling.

What am I doing wrong?