what does dmesg show?
does it make mention to it when you plug it in??
scsi0 : SCSI emulation for USB Mass Storage devices
Vendor: LEXAR Model: JUMPDRIVE Rev: 1.20
Type: Direct-Access ANSI SCSI revision: 02
SCSI device sda: 503808 512-byte hdwr sectors (258 MB)
sda: assuming Write Enabled
sda: assuming drive cache: write through
Attached scsi removable disk sda at scsi0, channel 0, id 0, lun 0
Attached scsi generic sg0 at scsi0, channel 0, id 0, lun 0, type 0
USB Mass Storage device found at 3
usbcore: registered new driver usb-storage
USB Mass Storage support registered.
Does a /dev/sda or something like that pop up?
If so, you should be able to mount it.
It should say something like the above