You cannot leave Encrypted Drives loaded when you exit CryptArchiver. You must close all open files on loaded Encrypted Drives before you can unload them and exit CryptArchiver.
Right click on the blue CryptArchiver secure icon in the taskbar, and select "Unload Drives and Exit" to quit the application.
In case you have a Windows Explorer window open, or if some application is still using a file on the Encrypted Drive, you will not be able to unload the drive. You can shut down all applications which may be using files from the Encrypted Drive.