Since upgrading to 3.4.1 I can't export pictures (masters or versions) nor can I create a vault. There may be other things I can't do, but just haven't discovered!
In both cases, when I select the action, nothing happens at all. After a while, the cursor is 'mine' again and it's as if I hadn't done the action. For the vault, I get the message about creating one, then click Continue - then... nothing.
I have not seen this error before. To check, if some setting in your User account is not consistent with the new version, try to export and to create a vault from a new user account - create one from the "System Preferences > Users & Groups" panel. Don't change any preferences when using the account.
If you can export from Aperture using the new account, check the following
Have you export presets defined? Then quit Aperture and remove the file
~/Library/Application Support/Aperture/Import Presets.plist from your user library. try again to export.
Have you export plug-ins installed? Check with the manufacturers website, if these plug-ins are compatible with Mt. Lion and install updated versions, if necessary. If no updated versions are available, deinstall them.
Your vault-problem: Is the vault on an external volume? How is it formatted? Is it a local volume or network voume? Have you checked the permissions? Can you create a vault on your system drive?
Do you use file-vault in your user account?
Be sure to make a Time machine backup of your aperture library, as long as you cannot create vaults.
Regards
Léonie