That is a strange one. I want to say cookies weren't being retained right but I can't be sure.
I still can't log in today w/o using proxy - guess it's now probably a permanent thing for me due to some unknown reasons. BTW, I've also encountered a strange, never-before-seen phenonmenon while editing an article today: the system automatically deleted a certain part (more precisely, the character string ":80") of the article after I saved my edits, & when I tried adding it back, it kept ignoring it & didn't save it, tho I've managed to get around that in the end. It's pretty bizarre - hope it's just an isolated incident due to some by-chance anomalies.