These days Google has some connectivity problems (even their main website Google.com and GMail) in my
country at least!
and since SO depends on jQuery from ajax.googleapis.com, FireFox shows waiting for
ajax.googleapis.com... and hangs there...
Are you considering loading your own hosted JS files, which does not affect site operations I guess?
I can't comment, I have no tag lookup, I can't see my notifications...etc.
UPDATE 22 Apr: I'm observing the same situation currently (actually, for several hours already).