Hm. Still not working for me in FF. My guess is it's a local issue, but I don't know what it would be that would cause both FF and Chrome to mess up...
Could a broken HTTP proxy be in your way? You can look at your HTTP traffic in Chrome by hitting F12 and clicking on the 'Network' tab, or in Firefox by installing the HttpFox addon. You can click around on the requests/responses and see if you're getting any strange error responses.
Also, have you tried ctrl-shift-r to force reload in both browsers? Some broken resource might be cached.
Tried Ctrl-shift-R. Didn't work. I didn't really do anything, but it seems to be working now. Very strange set of circumstances though. Neither FF or Chrome would process any AJAX on any site.
I tried in FF 8.0
I'm using Firefox 8.0.
I tried in FF 8.0 and Chrome 15.0, and couldn't post, but it worked in IE9. Anyone else having this problem?