I did a MOSS build recently and came across these three errors on my production 64bit based server farm. This error occurs in different formats. If you look at the event log it "may" register the following:

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Event 6398
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Event Type:    Error
Event Source:    Windows SharePoint Services 3
Event Category:    Timer
Event ID:    6398
Date:        25/10/2007
Time:        1:49:18 p.m.
User:        N/A
Computer:    WLGSVR001
Description:
The Execute method of job definition Microsoft.Office.Server.Search.Administration.IndexingScheduleJobDefinition (ID 00ef0f9d-dfec-449c-b1e8-b94f4d40cea1) threw an exception. More information is included below.

Retrieving the COM class factory for component with CLSID {3D42CCB1-4665-4620-92A3-478F47389230} failed due to the following error: 80070005.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

And the other two errors (6482 and 7888) are sometimes related to a COM class error or a Search component failure related error. This seems to be an error that comes up with 64bit environments. There is a HOTFIX available via connect. The error relates to Microsoft .Net Framework 2.0.

The KB article is here: http://support.microsoft.com/kb/923028/en-us

You should only apply this fix for servers that have this specific error. The Hot Fix is available on Connect using Live ID

Hot Fix: 923028

https://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=6003

I had to restart the Search service once I applied the Hot fix. Gayan Peiris has also blogged earlier about this error.