What does "mount" executed in a terminal tell you?
Please execute "mount" without any parameter too.
intersect:~# mount
/dev/mmcblk0p2 on / type ext4 (rw,noatime)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
procbususb on /proc/bus/usb type usbfs (rw)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
intersect:~# mount 192.168.2.200:/PUBLIC /hddext
mount.nfs: mount to NFS server '192.168.2.200' failed: System Error: Connection refused