Unmounting a deleted ISO.

[subsystems]

I ran into a dumb problem. VirbualBox 2.2.4
I was running XP as a client and had mounted an ISO as a DVD. I wanted to see how Windows Media Player played a movie.
To save client boot times I have been Saving the client with the client desktop running.
All is well until I forgot I had mounted and ISO in an XP client and later deleted the ISO file.
Now VirtualBox won't let the XP client launch because the mounted file doesn't exist.

When I try to release the file it complains that the XP client still has it mounted and displays a message saying it failed to unmount the file with an error #2.

I was able to fix it by putting the ISO file back where it was, then VirtualBox would let the XP client start. Once it was running I was able to unmount the DVD image and remove it from the media manager. Now I could go back and again delete the ISO file without further problems.

As a test, I started the XP client again, mounted an actual DVD, opened My Computer and a second with the DVD files displayed.
I then Saved the XP Client. Once it was no longer running I ejected the DVD. Now I restarted the XP client with no errors.
When the desktop came up the DVD simply went into an ejected state in both windows. This is what I would expect.

Why isn't the same true for a mounted ISO that is deleted while the Client is off?
Shouldn't VirtualBox treat it the same as an actual ejected disk?