I came across this error in SharePoint yesterday. It seemed to spontaneously occur for no reason I could figure out and seemed to be linked to importing user profiles from Active Directory. The import stopped working and this error started to appear.
After searching I found a few articles suggesting to fix permissions on the OSearch component. One of these is http://www.sharepointblogs.com/jasonmedero/archive/2008/02/08/after-applying-moss-2007-sp1-event-log-error-retrieving-the-com-class-factory-for-component-with-clsid-3d42ccb1-4665-4620-92a3-478f47389230-failed-due-to-the-following-error-80070005.aspx
I checked these permissions and found that they were already correct. What I did try then was to stop and start the osearch service.
Restarting the osearch service made the error go away BUT then when I tried to go to the User Profile page in the SSP I got a new error which stated there was a problem connecting to the database or to the search. Upon further investigation I discovered that the SSP web application had lost it's connection to the indexer. Once I added this back in it seemed to work fine again.
