I was having problems installing guest additions on Ubuntu Lucid, with the following error:
Could not mount the media/drive '/usr/share/virtualbox/VBoxGuestAdditions.iso' (VERR_DEV_IO_ERROR)
The answer was to:
"Shut down the guest. Go to the storage section of the guest settings in the VBox program.
Click once on the CD/DVD and then on the right select empty in the drop down list.
Start the guest and then click on install guest additions."
With a little side of applesauce...
©2006 Shannon Eric Peevey