cannot write to usb drive

[Umarzuki Mochlis <umarzuki@gmail.com>]

umarzuki@ctrl:~$ sudo mount /dev/sdb1 /mnt/
mount: block device /dev/sdb1 is write-protected, mounting read-only
umarzuki@ctrl:~$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              11G  7.7G  2.2G  78% /
tmpfs                 1.9G     0  1.9G   0% /lib/init/rw
udev                   10M  904K  9.2M   9% /dev
tmpfs                 1.9G     0  1.9G   0% /dev/shm
/dev/sda2             123G  112G  5.3G  96% /home
/dev/sdb1             1.9G 1020M  892M  54% /mnt
umarzuki@ctrl:~$ df -hi
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/sda1               671K    180K    492K   27% /
tmpfs                   465K       4    465K    1% /lib/init/rw
udev                    465K    1.7K    463K    1% /dev
tmpfs                   465K       1    465K    1% /dev/shm
/dev/sda2               7.8M    123K    7.7M    2% /home
/dev/sdb1                  0       0       0    -  /mnt


It is /dev/sdb1. I could not find any write protection button on this
usb flashdrive. How can I make this one writeable again?

-- 
Regards,

Umarzuki Mochlis