I apologize in advance if this issue is already discussed in another thread - I could not find one so I decided to start it. Host OS: OS X 10.6.2, VBox Release: 3.1.2, Guest OS Windows XP SP2.
I inadvertently moved a mounted iso image file to the trash while it was attached to a VM (I believe the VM was NOT running at the time).
When I tried to start the VM it naturally gave me an error; I realized what I had done and I "put back" the image file I had erroneously moved to the trash. The VM started and appeared to work except I don't think I actually exercised the virtual DVD in question from the VM.
Later I decided I did not need that iso image any more so after unmounting it, I tried unattaching it from the VM using the Virtual Media Manager (VMM) GUI. VMM did not allow me to unattach the file and, therefore, did not let me delete it since it showed as attached to a VM.
No amount of playing with VBoxManage storageattach seemed to unattach the file so I hand-edited the VIRTUAL MACHINE's xml file, removing the <Image uuid=xxxxx /> under the <AttachedDevice type="DVD"...> </AttachedDevice> entry in the xml. That did the trick: the file did not show as attached in VMM and VMM allowed me to delete it from the VMM DVD file list.
This is not a big issue (other than a fair warning not to delete an attached file from the OS!...) but only an observation that somehow the VMM GUI breaks when you put back an attached file you moveed to trash. I can supply "before" and "after" VM xml files, but I don't think they convey any more info than the above verbal description.