You get the error message that your Outlook file is in use and cannot be accessed. As a result, you cannot access your email. The program will open, but Outlook will not open the associated .pst file, (email).
This issue is caused by the PST file being access by another program, such as backup software. There are two solutions for this. Either wait for the backup software to finish backing up, (Carbonite can take some time), or close the backup software using the Task Manager or closing the backup software from within that software.
Once that is done, wait a minute for the software to completely close and then try again. If this effort fails, close all programs and reboot the system. Immediately try to open Outlook upon reboot.
If a backup program, such as Carbonite, continues to cause this issue, you may consider another program to back up your software, change the time it backs up or temporarily stop the backup service.