The Google search ‘gmail “Your session has expired. Please sign in again.” ‘ reveals that a number of folks have experienced a broken cookie problem with Firefox 1.0 and gmail, but no evidence of it affecting Safari users.

Sadly, that means I am up a creek. Maybe Firefox has gotten speedier than the last time I used it.

UPDATE: It’s fixed itself, it seems. I’m still gonna check out Firefox again, as suggested by Mr. Harpel.