I'm fairly new to Linux and VirtualBox, so bear with me.
I installed Zorin OS and then Guest Additions and it worked fine at first, but after I had updated all my packages it stopped working - I could no longer run it in Seamless mode. If I tried to re-install GA, it said "Unable to mount the CD/DVD image [name of image] Would you like to force mounting of this medium?" Then underneath: "could not mount the media/drive [name] (VERR_PDM_MEDIA_LOCKED)"
The same thing happened with several Ubuntu-based distros I tried, most recently Lubuntu. It works fine prior to updating, but after that I just get error messages.
From the Terminal, I ran sudo sh /media/cdrom/VBoxLinuxAdditions.run, but it says 'Can't open'
Under 'Disks' it says it is mounted. Unmounting and ejecting then retrying doesn't help.
What am I doing wrong?
I'm running the standard "lubuntu-12.10-desktop-i386.iso" on OSX Mountain Lion, allocating 1gb RAM and 8gb disk space.