The Solr crawl db may be corrupt if you see the following:
- Clicking on Node Status gives an error 'ManifoldCF cannot communicate to the Solr crawl maintenance database..."
- HSQL java.exe process is missing from Process Explorer on the Solr server.
- ManifoldCF web page throws an error while navigating to Status and Job Management.
- New content isn't being indexed.
- The crawl doesn't appear to end.
Follow these articles to fix the reported behavior. Note that search is down while the crawldb is being rebuilt.