There is a bug in the 1.0 version that seems to be affect some customers that even after the purchase of Aerochive, it still reports that the trial version has expired. Here is what you can do to get it running.
When you get your serial number in the email do the following.
1) Make sure you have version 1.1.2 If you don't have 1.1.2, Download the update by using the menu item. "Check for Free Updates" under the Aerochive menu. If the menu item is disabled then go here to get version 1.1 and install it like you did initially: http://www.softwareops.com/downloads/Aerochive.dmg
2) After version 1.1 is installed, select the "View Registration Info..." under the Aerochive menu.
3) Enter this serial number in the field and click Register.
4) It should confirm that it registers.
5) Quit and restart Aerochive you should be back in business.
If it appears to be registered and still is still locked out then do this to start over. This usually does the trick. It will delete the existing backups so you will have to backup again.