Following can be the root cause of this error :
The machine has a high CPU load and the process takes a long time to start and fails to execute the CoRegisterClassObjects() in less than 120 seconds.
you run Office applications on the server side or any unattended application.
All current versions of Microsoft Office were designed, tested, and configured to run as end-user products on a client workstation. They assume an interactive desktop and user profile. They do not provide the level of reentrancy or security that is necessary to meet the needs of server-side components that are designed to run unattended.
Microsoft does not currently recommend, and does not support, Automation of Microsoft Office applications from any unattended, non-interactive client application or component (including ASP, ASP.NET, DCOM, and NT Services), because Office may exhibit unstable behavior and/or deadlock when Office is run in this environment. Read more about that in the Considerations for server-side
Amit Kr. Anand