CRASH: filesystem went read only

[Richard Harran <95rmwh@eng.cam.ac.uk>]

I just had a huge panic, when my file system 'spontaneously' turned read
only!  I was using netscape (3.04), and all its windows vanished from
the screen.  I tried to restart it, and got the 'detected lock' message,
so I tried to 'rm' ~/.netscape/lock.  It told me:
	rm: lock: filesystem readonly.
(or words to that effect, unfortunately, I couldn't cut'n'paste, or
record them electronically, and forgot to write down all the messages,
sorry)

I tried removing this as root, and had the same problem, and found that
my entire filesystem was read-only.  Unfortunately, I had a very
important file that I had been editing all morning open in emacs.  I
also found I could not RTFM, or send emails, because these operations
needed to create tempory files.

Luckily, I remebered that I had a mounted dos partition, and I was able
to save my work on that, then re-boot.  On shutdown, I got an error
like:
	stopping system log daemon: warning failed to kill 107:
	no such process.
And on reboot, got all sorts of filesystem errors, which, hopefully
efschk has fixed.

Does anyone have any idea what could have caused this to happen, and
what I can do to prevent it from happening again. 

Thanks
Rich