Last evening I had installed updates on Ubuntu 12.04 and I realise this morning that the full screen function does not work anymore.
Everytime I click on VirtualBox window – Devices – Install Guest Additions, gives me an error (VERR_PDM_MEDIA_LOCKED)
Then I realised that I had to unmount the drive.
easy steps to do this
1. ‘Devices’ Drill down
2. ‘CD/DVD Devices’ uncheck VBoxGuestAdditions.iso
3. without restart, click on Devices again and ‘Install Guest Additions’
4. The terminal automatically starts , give your password… Might take a few minutes.