Yes Ive noticed this too, and that it doesn't happen on other boards. Ive also noticed that it doesn't happen on this board when I access it from some PCs.
So my guess is that it's as part of how the board was initially set up and uses the security settings as hold on the local PC.
Now, in knowing this it doesn't help much - and to be honest I'v got used to it now (Its been ages since I made a post as GUEST).
Basically I remember to login as that way I can esily get to see where all the new messages are
