I have a TS-7800, and it typically boots from the SD card inserted in it. When I tried to boot it up today, it hung on the syslog line. I am now having "Read only file system" problems. What has gone wrong?

Bootup console:

    >> Copyright (c) 2008, Technologic Systems
>> Booting from SD card...
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>> Booting to SD Card...
INIT: version 2.86 booting
Starting the hotplug events dispatcher: udevd.
Synthesizing the initial hotplug events...done.
Waiting for /dev to be fully populated...done.
mount: can't find / in /etc/fstab or /etc/mtab
Cleaning up ifupdown...rm: cannot remove `/etc/network/run/ifstate': Read-only file system
Loading kernel modules...done.
Checking all file systems...
fsck 1.37 (21-Mar-2005)
... done.
none on /dev/pts type devpts (rw,gid=5,mode=620)
/etc/init.d/rcS: line 39: /tmp/.clean: Read-only file system
Setting up networking...done.
Setting up IP spoofing protection: rp_filter.
Enabling packet forwarding...done.
Configuring network interfaces...ifup: failed to open statefile /etc/network/run/ifstate: Read-only file system
done.
Starting portmap daemon: portmap.
/etc/init.d/rcS: line 39: /tmp/.clean: Read-only file system
/etc/init.d/rcS: line 24: /var/run/utmp: Read-only file system
rm: cannot remove `/var/lib/urandom/random-seed': Read-only file system
urandom start: failed.
Recovering nvi editor sessions... done.
INIT: Entering runlevel: 3
Starting system log daemon: syslogd
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Starting kernel log daemon: klogd.
Starting MTA: open: Read-only file system
touch: cannot touch `/var/lib/exim4/config.autogenerated.tmp': Read-only file system
chown: cannot access `/var/lib/exim4/config.autogenerated.tmp': No such file or directory
chmod: cannot access `/var/lib/exim4/config.autogenerated.tmp': No such file or directory
chmod: changing permissions of `/var/lib/exim4/config.autogenerated': Read-only file system
/usr/sbin/update-exim4.conf: line 260: cannot create temp file for here document: Read-only file system
/usr/sbin/update-exim4.conf: line 387: /var/lib/exim4/config.autogenerated.tmp: Read-only file system
2002-01-01 01:31:36 Cannot open main log file "/var/log/exim4/mainlog": Read-only file system: euid=0 egid=0
2002-01-01 01:31:36 non-existent configuration file(s): /var/lib/exim4/config.autogenerated.tmp
2002-01-01 01:31:36 Cannot open main log file "/var/log/exim4/mainlog": Read-only file system: euid=0 egid=0
exim: could not open panic log - aborting: see message(s) above
Invalid new configfile /var/lib/exim4/config.autogenerated.tmp
not installing /var/lib/exim4/config.autogenerated.tmp to
/var/lib/exim4/config.autogenerated
Starting internet superserver: inetd.
Starting OpenBSD Secure Shell server: sshd.
Starting NFS common utilities: statdStarting periodic command scheduler: cron/usr/sbin/cron: can't open or create /var/run/crond.pid: Read-only file system
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Starting web server (apache2)...(30)Read-only file system: apache2: could not open error log file /var/log/apache2/error.log.
Unable to open logs
 failed!

Debian GNU/Linux 3.1 ts7800 ttyS0

ts7800 login: