Here's something I haven't run into in the past.
I went into my admin panel, did nothing (I poked through the pages, but I didn't change anything), went back to view my site.
After poking around the site, I wanted to change a permalinks option, I click Site Admin, and the the Throbber (What is a Throbber?) spins, then it simply times out.
However, I don't get a timeout page, the throbber just stops, and page essentially enters a 'done' status, still showing my site itself.
The funny thing is, I can get into the admin panel with a direct file link, or with the edit this links.
However, it appears that my Dashboard page is broken, because clicking the Dashboard link while in the admin panel exhibits the same behavior.
There's nothing in my error logs, so I'm unsure of how to go about debugging this.
(PHP4.4, Apache2, MySQL 4.1, Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b5) Gecko/20051006 Firefox/1.4.1)
(It occurs on my Firefox 1.0 at home as well.)