wheezy: / mounts readonly at boot, I can't figure out why

[Mike Linksvayer <ml@gondwanaland.com>]

http://gondwanaland.com/i/20120417-boot.png shows boot screen photo;
nothing is logged obviously

fsck finds no problems http://gondwanaland.com/i/20120417-fsck.png

mount -o remount,rw / works fine

(but I have to restart network-manager and gdm3 to get a usable
system; I'm not sure it is related, but I can't seem to connect to a
service running on localhost, eg python -m SimpleHTTPServer 8080 and
in another terminal w3m http://localhost:8080, w3m times out)

I don't notice anything amiss in fstab

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    defaults        0       0
# / was on /dev/sda1 during installation
UUID=2934c627-6f1a-438b-a877-1544108c7418 /               ext3
errors=remount-ro 0       1
# swap was on /dev/sda5 during installation
UUID=39b1f59e-6193-4c46-8b4d-80b183f0b19c none            swap    sw
           0       0
/dev/scd0       /media/cdrom0   udf,iso9660 user,noauto     0       0
/dev/sdb1       /media/usb0     auto    rw,user,noauto  0       0


Root filesystem mounted fine under squeeze, and after I upgraded to
wheezy. I've been living with it for a bit, so I'm not exactly sure,
but I think it started after doing a dist-upgrade on wheezy, but that
could be coincidence. The machine is a Lenovo T400 FWIW.

Any pointers would be much appreciated. Hopefully I'm doing something
obviously wrong and fixable, but if not any hints about how to debug?

Thanks,
Mike