USB Flash Drive auto mount failure-linux

I’m using Debian and I can’t access my USB flash drive. I’ve checked entries in both fstab and mtab files and they seem to be O.K. i have the following in fstab and mtab respectively:
usbfs /proc/bus/usb usbfs devmode=0666 0 0
usbfs /proc/bus/usb usbfs rw,devmode=0666 0 0

What could be the problem?