Bottom Left "My Cookies"
Click that and then you can clear / delete your cookies.
Maybe your members are referring to a private message e-mail?
When they get an e-mail the link to go and read that e-mail ends with =login?
Which takes them to the login page but there actually still logged in and only need to hit the forum list to get to the My Messages.
I'm pointing that one out as it was one that members got caught out with too.
Hope that help,
but see if you can get the "Details" from your members normally the answers isnt too far away
