It's possible that the application encountered an internal error. You can try reboots your device and try again opening it. If the error still appearing, try clearing the application's cache. To do this, from the menu of your device, go to Settings > Applications > Manage Applications > All tab > tap on Vault and select Clear Cache and Clear Data. By doing this, you will not lose any data from the application, but you might be able to recover your photos. If this will not fix your problem, there is no way to recover your photos, because they can't be accessed anymore.
