Cannot write to SD card

[Dotan Cohen]

I have a 2 GB Sandisk SD card that I often write to. Just today, it
has started to be mounted read-only:
cp: cannot create regular file `bg.jpg2': Read-only file system

The read-write switch on  the side of the card is set to write, and
I've never had trouble with it before. So I figured that I'll be smart
and man mount, in where I discovered the -w flag, but I get this
error:
[root at localhost ~]# mount -w /media/disk
mount: /dev/sda1 already mounted or /media/disk busy
mount: according to mtab, /dev/sda1 is already mounted on /media/disk

So I tried unmounting it, but the device seems to be busy:
[root at localhost ~]# umount /media/disk
umount: /media/disk: device is busy
umount: /media/disk: device is busy

There are no open konqueror windows, or anything else that might be
accessing the card, so far as I can tell. What must one do to either:
1) determine what is accessing the disk
or
2) Force umount anyway

Thanks in advance.

Dotan Cohen

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