I tried it too, and I learned that if the word you are searching is not found in the thread, you will not get that error -- it will just take you to a page that says the word wasn't found. If the word WAS found, you will get the DB error message.
The journal owner frequently mentions a friend named "Kathy" and on page 216 of the thread that name is mentioned 4 different times, yet if I search that thread for the word "Kathy" without the quotes I get no results.
In both cases I get a page that has the following message in it:
The following errors occurred with your search:
1. Sorry - no matches. Please try some different terms.
When I did an advanced search for Kathy it just came up with your post in this thread in the results
Yes, it seems to be hit or miss, some threads it works on, other threads it doesn't return as many posts as you would expect and in other cases it returns no results even though the word is in the thread.