Case: On Excel start up, you may receive the "Automation error" or "Automation error or Unknown error".
Solution:This happen because of Microsoft update. The notification can be solved by registering the file MSCOMCTL.OCX again.
- Go to [Start-run] on the system.
- If it's a 32 bits machine type the following: regsvr32 C:\windows\System32\MSCOMCTL.OCX
- If it's a 64 bits machine type the following: regsvr32 C:\windows\SysWOW64\MSCOMCTL.OCX
After doing this a notification will come that the file is correctly registered. If this is not the case and you get for instance the following notification
"MSCOMCTL.OCX' is loaded but the call to DllRegisterServer failed with error code 0x80004005.", this could be due to security issues on the system. If this is the case make sure the Windows "Dos Prompt / Command Prompt" is opened with "run as administrator". To do this go to [Start-all programs-accessoires] and click with right mouse on the "Command Prompt" and choose to run as administrator.
In the Command Prompt screen you can type the line (regsvr32 C:\windows\System32\MSCOMCTL.OCX for 32-bit or regsvr32 C:\windows\SysWOW64\MSCOMCTL.OCX for 64-bit) and press enter.
After the file is correctly registered opening Microsoft Excel will not show the notification anymore.