Some serious confusion in your paths.
You have a CF card which is mounted (by Zaurus convention) on /mnt/cf.
The CF card device is /dev/hda, the first partition, which is what you mount, is /dev/hda1
Make sure you are running as root for all of the commands below!
Therefore you should do (this assumes that it can automagically work out the partition type):
# mount /dev/hda1 /mnt/cf
If it can't work out the partition type then do:
# mount -t ext2 /dev/hda1 /mnt/cf
or
# mount -t fat16 /dev/hda1 /mnt/cf
or
# mount -t vfat /dev/hda1 /mnt/cf
depending on what you think the format is.
Assuming the fstab entry is correct, you can also get away with just doing:
# mount /mnt/cf
Si
P.S. Another option is to make sure it's not mounted (just run 'mount' on its own) and then run 'fsck /dev/hda1' to check the filesystem