Problem:

Recently our content source for the sharepoint sites no longer crawls and instead throws up the Error HRESULT E_FAIL has been returned from a call to a COM component

I had a look on the web and the only solution has been to change impersonation settings from false to true in the web config. Unfortunately ours was already set to true and I still have this error. Cannot get the crawl to work in sharepoint now.

Resolution:

Check the web application's website in IIS 7.

Under Authentication, make sure ASP.NET Impersonation is ENABLED. Mine was disabled and caused this error. If you have applications in SharePoint that need this disabled, you might want to extend the web application it another IIS website and Disable impersonation for users, keeping the default web application's zone enabled for search crawls on that URL.

Ensure this is set for each of the Web Applications that you wish to crawl.

Another common Crawl issue is using an AD service Account that has not been added to the SharePoint Managed Accounts.