The mystery is this: I run Firefox 3.07 on OS X 10.4.11 to access Gmail. A few days ago, out of the blue, I found I couldn't log in. I entered my user name and password and Gmail returned to the login screen without an error message or anything apparently amiss other than I was back where I started.

Oddly enough, I could log in from the same Mac using Safari 3.2.1, as I could using Firefox 3.0.7 on Windows XP SP2.

A friend suggested that the plugin could be the culprit as it sometimes causes problems, but although I had been using it I had disabled it for exactly that reason a few weeks before.

In fact, in trying to figure out what was wrong I had disabled all of the Firefox add-ons on my Mac but nothing changed -- I still couldn't log in. Even reinstalling Firefox didn't help.

Out of curiosity I thought I'd try to seek an answer using a new "social search" service (a search service combined with social networking) called .