I recently installed linux in a computer and I had a partition dedicated to /tmp. Mounting at boot time was not working.
The culprit was an extra / in my /etc/fstab:
/dev/sdb1 /tmp/ ext3 noexec,nosuid,nodev 0 2
I removed the / from /tmp/ and everything worked as expected… I guess in fstab, a mount point is expected, not a directory (small difference).
/dev/sdb1 /tmp ext3 noexec,nosuid,nodev 0 2