Hello Julian,
Why did the email addresses not autocomplete I do not know. It might have to do something with Espionage but so far nobody reported this to us.
However hanging on decryption is indeed an Espionage problem, and should have not happen.
But considering you were decrypting probably a considerable amount of data, could it be possible that you ran out of free space on your disk?
Was the Apple Mail quit when you tried to decrypt the folders?
Once you downloaded the Version 3, you probably overwrote the Version 2 with it, so unless you have to Espioange apps in your App folder, probably the one you have is V3 (you can check using get info).
If this is correct, quit Espionage 3 using the padlock in the menu bar (both 2 and 3 have padlocks, but the 3 has this new kind of window, with cog icon in the lower right corner, use that to quit it).
Then rename the app to something like Espionage3.
Go to the link
http://www.taoeffect.com/espionage/Espionage.dmg to download the version 2 again. Place it in your app folder and launch it.
Then you can try to decrypt again.
Once you have all your data back, you can uninstall it using the uninstall option in the Espionage menu.
In case you do not manage to launch Espionage, or the folders do not show in the list, let me know if you get a pass prompt when you click on the protected folder or you enter into the folder and see 3 subfolders named "this folder contains..." and I will instruct you further.
Rgds
Zsolt