I have a Windows Server 2003 running WSS 3.0 that has started displaying "Service Unavailable" when I try to open the Central Administration page. I also get the following errors in the Event Viewer:

"The start address <sts3://servus-rkfdsp/contentdbid={126e686a-71da-426f-a5b1-102b6cd50f44}> cannot be crawled.

Context: Application 'Search index file on the search server', Catalog 'Search'

Details:
Access is denied. Check that the Default Content Access Account has access to this content, or add a crawl rule to crawl this content. (0x80041205)"

"The update cannot be started because the content sources cannot be accessed. Fix the errors and try the update again.

Context: Application 'Search', Catalog 'index file on the search server Search'"

"The Execute method of job definition Microsoft.SharePoint.Administration.Backup.SPBackupRestoreJobDefinition (ID 04a4cfe1-309c-479c-940b-e262ae9f4c23) threw an exception. More information is included below.

The backup job failed. For more information, see the error log that is located in the backup directory."

I have tried everything that I have found in the support center (find the assembly, run Repair) with no success. I cannot replce the assembly which I can't find anywhere. Has anyone else had this happen, and fixed it?