I've upgraded a very old site from 1.4.1 to 1.9.2. The database seems to have upgraded properly. But now all the catalog searches just ignore the search criteria and bring back everything. Even the quick search box brings up everything.
When I entered a search term in the quick search box, it prompted me with what looked like a correct count. But when I ran a search with the search term, the next time I entered the same term, it prompted me with a count of all the items.
Why is the catalog search ignoring the search criteria, and what can I do to fix the searches?