usb only mounted read-only?

[Roger Grosswiler]

hey,

i have no more privileges to write on my usbstick. it seems, i have no
more rights?

rog

mount says: 
/dev/sda on /media/MPIO-1 type vfat (rw,noexec,nosuid,nodev)

dmesg says:
usb 1-1: new full speed USB device using uhci_hcd and address 8
scsi1 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 8
usb-storage: waiting for device to settle before scanning
  Vendor: MPIO      Model: FY200             Rev: 1000
  Type:   Direct-Access                      ANSI SCSI revision: 00
SCSI device sda: 1015809 512-byte hdwr sectors (520 MB)
sda: Write Protect is off
sda: Mode Sense: 45 00 00 08
sda: assuming drive cache: write through
SCSI device sda: 1015809 512-byte hdwr sectors (520 MB)
sda: Write Protect is off
sda: Mode Sense: 45 00 00 08
sda: assuming drive cache: write through
 sda:
sd 1:0:0:0: Attached scsi removable disk sda
usb-storage: device scan complete
SELinux: initialized (dev sda, type vfat), uses genfs_contexts
FAT: Filesystem panic (dev sda)
    fat_get_cluster: invalid cluster chain (i_pos 0)
    File system has been set read-only