Virtual Box UUID {07c3………} does not match the value {2c1b…} stored in the media registry

Here’s what fixed this error for me (using VirtualBox 4.3):

1. Go to File → Virtual Media Manager
2. In the Hard drives tab, you should see a red exclamation point icon beside the disk image you’re having trouble with. Select it → Release → Remove → Close.
3. Go back into the settings for the VM and re-add the disk.

To prevent the error in the future, before deleting the virtual disk image files, remove them from the Virtual Media Manager:

1. Go to File → Virtual Media Manager
2. In the Hard drives tab, find the virtual disk you want to remove, select it → Release → Remove → Keep (or Delete if you want to delete it permanently) → Close.
3. Go back into the settings for the VM and readd the disk.