Hmmm.. I gonna guess that youre using Firefox.
I use Firefox on 2 PCs at home and IE at work.
With Firefox, I also have the issue with the massive blank screen. No answer for that.
The large amount of blank also happens when I go to the messages section.
As for the auto login, I have found that on one PC at home (old Windows Me system), the first page I come to shows me as not logged in.
I then would login and say for keeps.
Next time I come to the site, it again shows me as not logged in, but when I select a link to another part of the site, it does show me as logged in, so I think it is possibly a cookie issue.
With IE, I do not get either issue.