SharePoint 2010 Crawl stopped working

Hello

I'm seeing "Access is denied. Verify that either the Default Content Access Account
has access to this repository, or add a crawl rule to crawl this repository. If
the repository being crawled is a SharePoint repository, verify that the account
you are using has "Full Read" permissions on the SharePoint Web Application
being crawled." in SharePoint search service. I'm not sure why it stopped working all of sudden. Truly appreciate any pointers.

Thanks

Manohar