Apparently things have started working again. I don't think I had any issues on my Mac when I was at home, but I will double check.
If it helps I believe it was tied to the updates to the 'wordpress' dashboard (so not my blog dashboard, but the part when you log into wordpress.com). Ever since that changed visually I have had issues on this computer - including the update of the views/visitors which appeared yesterday.
I just tested a preview post and it appears to be working, as does my problem with being forced to log-in on other wordpress hosted sites. Hopefully it's resolved itself.
I will double check when I get home on my Mac.