THe original problem of this is related to work I was doing in a ticket with him. We've got users accessing both the www and the non-www urls which doesn't work too well. So we've been working on a redirect to make sure they always access the same URL. I'm pretty sure this is related to the redirect as they may be logged in with the old bookmark, but not after the redirect and then you get cookie conflicts.
So, basically they need to clear out their cookies and update any bookmarks to the proper URL. Meaning if your FULL URL is set to
www.domain.com, they need to bookmark
www.domain.com. If FULL URL is only domain.com then they need to boomark just domain.com.
Hopefully that makes a bit of sense.
