USB stick automatically mounted read only?

[Daan]

When I insert my USB stick into my Debian Etch computer, it gets automatically mounted, however, it gets mounted read only. At least, that is what mkdir complaints about. But /etc/mtab says rw, which I think means read and write, so I don't get it.

daan@thrix:/media/KINGSTON$ mkdir tst
mkdir: cannot create directory `tst': Read-only file system
daan@thrix:/media/KINGSTON$ ls -l -d ../KINGSTON/
drwx------ 3 daan daan 16384 1970-01-01 01:00 ../KINGSTON/
daan@thrix:/media/KINGSTON$ cat /etc/mtab | grep KING
/dev/sda1 /media/KINGSTON vfat rw,noexec,nosuid,nodev,quiet,shortname=mixed,uid=1000,gid=1000,umask=077,iocharset=utf8 0 0
daan@thrix:/media/KINGSTON$

What can I do to mount it in way that I can write to it?
How do I get Debian to do that automatically?

I'm using Debian Etch and Gnome.

[Daan]

Hmm. I've been able to mount the device with the options specified in mtab and write to it. However, when I copied a large amount of data I got an error. That also happens when I am in Windows: it says it cannot find the specified file. Changing USB ports doesn't help. Reformatting doesn't help.