I have a D-Link DNS-323 network drive which mounts at multiple points to my filesystem when booting. I had to make some fstab changes when I upgraded from 11.2->11.3 last year, and now the same thing seems to be happening since I’ve upgraded to 11.4.
When I login to my profile the desktop hangs and no icons appear. I cannot open a Nautilus window, or access ALT-F2, however just about every other program works fine.
Since I disabled the fstab lines (slightly modified when copied here to generalize):
I guess you have solved your issue. Do some tests to see if it is stable now. If it fails, copy the message you get from the terminal command and paste it here.
The message you posted means:
the share is already mounted. rotfl!
or
if the share is not mounted, mtab contains corrupt data.