Debian Sparc4 mounts root as read-only

[Antti.Roppola at brs.gov.au]

Some time in the recent past, my Sparc4 has started
mounting root as read-only. /tmp and /var seem OK.

dmesg says:
VFS: Mounted root (ext2 filesystem) readonly.

fstab says:
/dev/sda1	/		ext2	defaults,errors=remount-ro	0	1

I tried "mount / -o remount,rw", but to no (discernable)
effect. When I display the partition table in fdisk, I notice
that Flag is set as "u" on root, but not swap. I can use
cat & echo to create and append to files, but not vi.

Anyone have any ideas on what is going on? It seems a reasonably
common problem (trolling Google), but I haven't yet found a fix.

TIA,

Antti