mount - CD-ROM issues in Kubuntu 15.04

I recently upgraded from Kubuntu 14.10 to 15.04. Since then, I cannot use my CD drive. If I insert a CD, it doesn't appear on my devices list. If I try mounting it, I get the following error:

% sudo mount /dev/cdrom a
mount: /dev/sr0 is write-protected, mounting read-only
mount: /dev/sr0: can't read superblock

Exactly specifying the filesystem doesn't work either.

% sudo mount -t iso9660 /dev/cdrom a

mount: /dev/sr0 is write-protected, mounting read-only
mount: wrong fs type, bad option, bad superblock on /dev/sr0,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.

I tried with an audio CD, a CD with files on it, and a DVD with files, and all of them result in the same problem.

To find the source of the problem, I tried the following:

• The same mount command when no CD is inserted gives the message that no medium found in the drive. So the system can detect the drive, it seems to have issues mounting the filesystem.


• Boot from a pen drive with the installation image of Kubuntu 15.04. It has the same issue.


• Boot from a pen drive with the installation image of Kubuntu 14.10. It can detect the CD.


• Install a kernel from 14.10 (following instructions from here), and try to boot with it. It is less surprising that X cannot start up, but when I try to mount the CD from the console, I get the same error message.


• Connect the CD drive to a different SATA port. Needless to say, it doesn't work.


• Try to play an audio CD with VLC. It works.

The contents of my /etc/fstab is:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
#                

# / was on /dev/sdb1 during installation
UUID=eaffd746-3d3d-4d1a-984f-7a795c379289 /               ext4    errors=remount-ro 0       1
# /home was on /dev/sdb2 during installation
UUID=b14350d3-2e8a-42ac-8804-3395eafd5c18 /home           ext4    defaults        0       2
# /local was on /dev/sda2 during installation
UUID=0407f630-5f45-411d-8f61-39fbfc1cb52b /local          ext4    defaults        0       2
# /windows was on /dev/sda3 during installation
UUID=5076310E7630F5F6 /windows        ntfs    defaults,umask=007,gid=46 0       0
# swap was on /dev/sdb5 during installation
UUID=163343d7-5880-479b-ac95-ab4f893652f8 none            swap    sw              0       0

Any ideas on how to fix this?